Method and apparatus for electrodeionization layered chambers

ABSTRACT

The present invention relates generally to the deionization of liquids through the use of electrodeionization methods and apparatuses. The apparatuses may be configured to minimize the fouling of the electrode chambers and to provide continuous regeneration of the ion exchange materials. The apparatuses may be configured according to the desired levels of deionization for anions, cations, or both. Finally, methods are presented for various uses of the apparatuses.

FIELD OF THE INVENTION

This invention relates generally to the field of deionization ofliquids, in particular to water purification through deionization. Morespecifically, the present invention pertains to electrodeionization(EDI) apparatuses and various methods of using the same, directingliquid through the apparatuses in different ways to achieve differentdeionization characteristics.

BACKGROUND OF THE INVENTION

Electrodeionization (EDI) is known in the art as a process which removesionized species from liquids, such as water, using electrically activemedia and an electric potential to influence ion transport. Examples ofelectrically active media comprise ion exchange materials and ionexchange membranes. In general “ion exchange materials” denotes solid(perhaps highly porous) materials that, when brought into contact with aliquid, cause ions in the liquid to be interchanged with ions in theexchange material. “Ion exchange membrane” or “ion selective membrane”generally denotes a membrane porous to some ions, perhaps containing ionexchange sites, and useful for controlling the flow of ions across themembrane, typically permitting the passage of some types of ions whileblocking others. In general, ion exchange membranes selectively permitthe transport of some types of ions and not others, and also block thepassage of the bulk liquid carrying the ions. A combination of ionselective membranes and ion exchange materials are sandwiched betweentwo electrodes (anode (+) and cathode (−)) under a direct current (DC)electric field to remove ions from the liquid. The electric field may beapplied in a continuous manner or may be applied in an intermittentmanner. Cation exchange materials (or cation materials for short) can beused to remove positively charged ions, such as calcium, magnesium,sodium, among others, replacing them with hydronium (H₃₀ ⁺ or H⁺) ions.Anion exchange materials (or anion materials for short) can be used toremove negatively charged ions, such as chloride, nitrate, silica, amongothers, replacing them with hydroxide ions. The hydronium and hydroxideions may subsequently be united to form water molecules. Eventually, theion exchange materials become saturated with contaminant ions and becomeless effective at treating the liquid. Once these materials aresignificantly contaminated, high-purity liquid flowing past them mayacquire trace amounts of contaminant ions by “displacement effects.” Inconventional deionization, the saturated (or exhausted) ion exchangemedia must be chemically recharged or regenerated periodically with astrong acid (for cation materials) or a strong base (for anionmaterials). The process of regenerating the ion exchange media withconcentrated solutions of strong acids or strong bases presentsconsiderable cost, time, safety, and waste disposal issues.

Continuous electrodeionization (CEDI), a subset of EDI, uses acombination of ion exchange materials and ion exchange membranes, anddirect current in a manner so as to continuously deionize liquids andalso to eliminate the need to chemically regenerate the ion exchangemedia. The “continuous” label of CEDI applies to the condition whereinthe electric field may be applied to the apparatus in a continuousmanner while product liquid is being produced. CEDI includes processessuch as continuous deionization, filled cell electrodialysis, orelectrodiaresis. The ionic transport properties of electrically activemedia are an important separation parameter.

In the EDI apparatus illustrated FIG. 1, contaminant ions migratethrough the ion depletion chambers 103, 107 and into the electrodechambers 101, 109. The ion exchange material in the composite beddepletion chamber 105, anion depletion chamber 103 and cation depletionchamber 107 are regenerated by water splitting in the composite beddepletion chamber 105. Hydronium produced from water splitting migratestowards the cathode passing though the cation exchange membrane 106 ofthe composite bed depletion chamber 105, into the cation depletionchamber 107 and ultimately into the cathode chamber 109. Similarly,hydroxide produced from water splitting migrates towards the anodepassing though the anion exchange membrane 104 of the composite beddepletion chamber 105, into the anion depletion chamber 103 andultimately into the anode chamber 101. Electrochemically producedhydronium, which results from oxidation of water at the anode, maintainselectroneutrality as hydroxide and contaminant anions migrate into theanode chamber. Similarly, electrochemically produced hydroxide, whichresults from the reduction of water at the cathode, maintainselectroneutrality as hydronium and contaminant cations migrate into thecathode chamber. In the apparatus illustrated in FIG. 1, the feed waterhardness must be less than about 1-2 parts-per-million (ppm) (as CaCO₃),otherwise precipitation of calcium as calcium carbonate or magnesium asmagnesium hydroxide may occur in the cathode chamber causing an increasein device resistance or an increase in the backpressure, decreased flow,and potential plugging in the apparatus. By flowing the electrode rinsefirst through the anode chamber and then through the cathode chamber,the hardness problem may be reduced since the anode electrode rinse isslightly acidic and thus will help minimize precipitation of calciumcarbonate and magnesium hydroxide. Still, feed water with hardness aboveseveral ppm (as CaCO₃) can cause problems in the apparatus. Anotherpotential problem with this apparatus can occur in the anode chamber.Common anions such as chloride and nitrate can be oxidized in the anodechamber to form electrochemically active species (ClO₂ and NO₂,respectively). These electrochemically active species can damage the ionexchange material in the anode chamber resulting in decreased lifetimeof the EDI apparatus.

Thus, there is a need for an EDI apparatus which reduces or overcomesproblems arising from electrode fouling by precipitation or damage tothe ion exchange materials of the electrode compartment byelectrochemically active compounds (such as oxidizers) while maintainingsome or all of the advantages of homogeneous-material ion depletionchambers.

FIG. 1 illustrates an EDI apparatus that may be used for “generalpurpose” liquid deionization. The apparatus comprises three iondepletion chambers, 103, 105, 107, and two electrode chambers, 101, 109,separated by four ion exchange membranes, 102, 104, 106, and 108. Thisconfiguration offers improved deionization capability but may addadditional complexity or cost for applications where the deionizationrequirement is selective. For some applications, the required waterpurity may require the exhaustive removal of anions or cations, but notboth. This is the case in many forms of chemical analysis where aspecific element or ion or a group of elements or ions are of interest.For example, in ion chromatography, either anions or cations aretypically analyzed using different chemistries. For anion analysis byion chromatography, the water used to prepare eluent or dilute samplesor standards should be free of all anions as any anion in the water willlikely manifest itself and either affect calibration (non-zerointercept) or compromise detection by increasing backgroundconductivity. Other examples requiring feed water sources free fromspecific ions are silicate analyzers, sodium analyzers or phosphateanalyzers as typically used to monitor high purity water. In theseapplications, the primary requirement is that the feed water hasconcentrations of the analyte(s) at or near the lowest possible levels,typically sub-ppb (part-per-billion) or ppt (part-per-trillion). Sincemany of these analyzers are used on-line (continuous analysis), it isdesirable to have a continuous, highly purified feed water source forthe analyzer. Currently, there are no commercially available waterpurifiers which can easily interface with analytical instruments andsupply feed water with extremely low contaminant levels of the analyteions. Therefore, there is a need for a simple, cost-effective EDIapparatus that may be devoted to a specific purpose.

SUMMARY OF THE INVENTION

Accordingly and advantageously the present invention discloses methodsand apparatuses that may address one or more of the issues discussedabove. In some embodiments of the present invention, a composite bedconcentrate chamber is used to collect and remove the contaminant ionsfrom the liquid. The contaminant ions are hindered from entering theelectrode chamber, thus reducing the electrode fouling associated withconventional EDI apparatuses.

In other embodiments of the present invention, the ion exchangeefficiency of chambers including homogeneous ion exchange materials maybe combined with the benefits of chambers or layers including compositeanion-cation ion exchange materials to produce liquids with very lowconcentrations of contaminant ions. In some embodiments of the presentinvention, the interface between adjacent layers may be transverse tothe applied electric field. In some embodiments of the presentinvention, the interface between adjacent layers may be parallel to theapplied electric field.

These and other advantages are achieved in accordance with the presentinvention as described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. The drawings are not to scale and the relative dimensionsof various elements in the drawings are depicted schematically and notto scale.

In the configurations disclosed below, liquid streams flow through theelectrode chambers and “concentrate” chambers. In the followingconfigurations, the electrode chambers may act as concentrate chambersor as a source of hydronium and hydroxide ions for regeneration of theion exchange materials. As concentrate chambers, contaminant ions mayeventually migrate into the electrode chambers (under the force of theapplied electric field) and may be removed from the electrode chamber bya liquid flow stream. The electrode chamber flow streams may typicallybe directed to waste. For simplicity of the drawings, the electrodechamber rinse streams and concentrate chamber rinse streams are notshown.

The techniques of the present invention may be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic representation of a EDI configuration.

FIG. 2 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 3 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 4A and FIG. 4B are schematic representations of EDI configurationsof embodiments of the present invention.

FIG. 5A and FIG. 5B are schematic representations of EDI configurationsof embodiments of the present invention.

FIG. 6 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 7 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 8 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 9 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 10 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 11 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 12 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 13 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 14 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 15 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

FIG. 16 is a schematic representation of an EDI configuration of oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Abbreviations and Definitions

The following abbreviations and definitions are used herein:

The abbreviation “EDI”=electrodeionization;

The abbreviation “CEDI”=continuous electrodeionization;

The abbreviation “IC”=ion chromatography;

The abbreviation “AM”=anion exchange membrane;

The abbreviation “CM”=cation exchange membrane;

The term “applied electric field” is understood to be the electric fieldarising from a voltage applied between the anode and the cathode withinthe EDI apparatus.

In FIGS. 1-16, the anode chamber has been labeled as “anode” forbrevity.

In FIGS. 1-16, the cathode chamber has been labeled as “cathode” forbrevity.

The term “depletion chamber” is defined as a chamber through which theproduct liquid stream flows during one of the steps of the process. Adepletion chamber may be filled with one of a homogeneous volume ofanion exchange material, or a homogeneous volume of cation exchangematerial, or a mixed ion exchange material, or a doped anion exchangematerial, or a doped cation exchange material, or may be comprised of“layers” of various ion exchange materials.

The abbreviation “LDC”=layered depletion chamber is a specific type of“depletion chamber” and is defined as a chamber that comprises “layers”of various ion exchange materials wherein the liquid to be processedflows through the layers in a sequential manner.

The term “concentrate chamber” is defined as a chamber wherein theproduct liquid stream does not flow. Typical examples of a concentratechamber include an electrode chamber (either anode or cathode), ananodic concentrate chamber (a chamber located adjacent to the anodechamber and separated therefrom by an ion exchange membrane), or acathodic concentrate chamber (a chamber located adjacent to the cathodechamber and separated therefrom by an ion exchange membrane), or aconcentrate chamber (wherein the concentrate chamber is not adjacent toan electrode chamber), among others. Typically, in some embodiments ofthe present invention, the electrode chambers (either anode or cathode),are not filled with ion exchange material. A concentrate chamber may befilled with a mixture of anion and cation exchange material, or a dopedanion exchange material, or a doped cation exchange material.

The term “mixed ion exchange material” is defined as a mixture of anionand cation exchange materials wherein the anion exchange material isresponsible for about 50% of the total ion exchange capacity and thecation exchange material is responsible for about 50% of the total ionexchange capacity. The term “mixed ion exchange material” also refers toa chamber that contains a mixture of anion and cation exchange materialswherein the anion exchange material is responsible for a range of about40% to about 60% of the total ion exchange capacity and the cationexchange material is responsible for the balance of the total ionexchange capacity. This definition is meant to be consistent with theconventional understanding of a “mixed bed” as containing a 50/50mixture of anion/cation ion exchange materials as well as a small range,typically from ˜40% to ˜60% on either side of the 50/50 mixture.

The abbreviation “ACC”=anodic concentrate chamber which is defined as aconcentrate chamber adjacent to the anode and separated from the anodeby an ion exchange membrane. The ACC may contain a homogeneous volume ofanion exchange material, or a homogeneous volume of cation exchangematerial, or a mixed ion exchange material, or a doped anion exchangematerial, or a doped cation exchange material. This is a chamber whereinthe product liquid stream does not flow.

The abbreviation “CCC”=cathodic concentrate chamber which is defined asa concentrate chamber adjacent to the cathode and separated from thecathode by an ion exchange membrane. The CCC may contain a homogeneousvolume of anion exchange material, or a homogeneous volume of cationexchange material, or a mixed ion exchange material, or a doped anionexchange material, or a doped cation exchange material. This is achamber wherein the product liquid stream does not flow.

The abbreviation “ADC”=anion depletion chamber is defined as a chamberthat typically includes therein a homogeneous volume of anion exchangematerial. These chambers have been labeled as “anion bed” in the legendof FIGS. 1-16 for brevity.

The abbreviation “CDC”=cation depletion chamber is defined as a chamberthat typically includes therein a homogeneous volume of cation exchangematerial. These chambers have been labeled as “cation bed” in the legendof FIGS. 1-16 for brevity.

The abbreviation “CBCC”=composite bed concentrate chamber. A compositebed concentrate chamber may be filled with a mixed ion exchangematerial, or a doped anion exchange material, or a doped cation exchangematerial.

The abbreviation “ACBCC”=anodic composite bed concentrate chamber isdefined as the composite bed concentrate chamber adjacent to the anodeand separated from the anode by an ion exchange membrane. The ionexchange membrane may be an AM or a CM. The ACBCC chamber may be filledwith a mixed ion exchange material, or a doped anion exchange material,or a doped cation exchange material.

The abbreviation “CCBCC”=cathodic composite bed concentrate chamber isdefined as the composite bed concentrate chamber adjacent to the cathodeand separated from the cathode by an ion exchange membrane. The ionexchange membrane may be an AM or a CM. The CCBCC chamber may be filledwith a mixed ion exchange material, a doped anion exchange material, ora doped cation exchange material.

The abbreviation “ACBDC”=anodic composite bed depletion chamber isdefined as the composite bed depletion chamber adjacent to the anode andseparated from the anode by an ion exchange membrane. The ion exchangemembrane may be an AM or a CM. The ACBDC chamber may be filled with amixed ion exchange material, or a doped anion exchange material, or adoped cation exchange material.

The abbreviation “CCBDC”=cathodic composite bed depletion chamber isdefined as the composite bed depletion chamber adjacent to the cathodeand separated from the cathode by an ion exchange membrane. The ionexchange membrane may be an AM or a CM. The CCBDC chamber may be filledwith a mixed ion exchange material, a doped anion exchange material, ora doped cation exchange material.

The abbreviation “CBDC”=composite bed depletion chamber is defined asthe composite bed depletion chamber that is not adjacent to either thecathode chamber or the anode chamber. The CBDC chamber may be filledwith a mixed ion exchange material, or a doped anion exchange material,or a doped cation exchange material.

The terms “dopant” and “doping agent” refer to a material that is addedto another material. In EDI, a dopant typically includes materials suchas an inert material, an electrically active non-ion exchange material,ion exchange materials, or mixtures thereof. Typically, ion exchangematerial, such as anion exchange materials or cation exchange materialsis added to a volume of the opposite ion exchange materials to adjustthe electrical conductivity. In some instances, doping of ion exchangematerials facilitate the transport of contaminant ions or may providefor water splitting which can produce regenerant ions (hydronium andhydroxide).

The term “doped cation exchange material” is defined as a composite ofanion and cation exchange materials wherein the cation exchange materialis responsible for at least about 60% of the total ion exchange capacityand the remainder of the total ion exchange capacity is contributed byanion exchange material. That is, the mixture is primarily a cationexchange material. This definition is meant to distinguish a “dopedcation exchange material” from the conventional understanding of a“mixed ion exchange bed” (or material)”. That is, “mixed ion exchangematerial (or bed)” is used herein to denote a bed having approximatelyequal cation and anion ion exchange capacities (typically equal towithin about ±10%) while “doped cation exchange material” denotes an ionexchange material in which cation exchange clearly predominates and theanion exchange material is a “dopant” or minority contributor. The dopedcation exchange material may be advantageous in that they can be used toalter the conductivity through the EDI apparatus and improve theperformance of the EDI apparatus.

The term “doped anion exchange material” is defined in a complimentarymanner to “doped cation exchange material” described above. That is,“doped anion exchange material” is a composite of anion and cationexchange materials wherein the anion exchange material is responsiblefor at least about 60% of the total ion exchange capacity and theremainder of the total ion exchange capacity is contributed by thecation exchange material. That is, the mixture is primarily an anionexchange material. This definition is meant to distinguish a “dopedanion exchange material” from the conventional understanding of a “mixedion exchange bed”. The doped anion exchange materials may beadvantageous in that they can be used to alter the conductivity throughthe EDI apparatus and improve the performance of the EDI apparatus.

The terms “hard” and “hardness” when used in reference to water,indicates water that contains concentrations (typically expressed inparts-per-million, (ppm)) of various minerals, such as calcium andmagnesium carbonates, bicarbonates, sulfates, or chlorides. The presenceof such dissolved minerals typically arises from prolonged contact withrocky substrates and soils. Such hardness in water tends to discolor,scale, and corrode materials.

The term “scale” refers to a solid deposit on a surface in contact witha liquid in which the deposit includes mineral compounds present in theliquid, e.g., calcium carbonate.

The term “water splitting” refers to the hydrolysis of water tohydronium and hydroxide ions, which occurs at the interface of anionexchange materials and cation exchange materials in the presence of anelectric potential. This is not a true electrochemical process, anddiffers from the electrolysis of water at an electrode in that watersplitting does not produce hydrogen or oxygen gas whereas conventionalelectrolysis of water produces both gases.

The terms “eluant” and “eluent” refer to a substance used to effect theseparation of ions from a separation column in an elution process.Examples of eluents include, but are not limited to, an acid or a base.

The term “elution” refers to the process of using an eluent to extractions from a separation column.

The term “eluate” refers to the product or substance that is separatedfrom a column in an elution process.

After considering the following description, those skilled in the artwill clearly realize that the teachings of the invention can be readilyutilized in liquid purification, specifically deionization, through theuse of various EDI apparatuses and methods in various ways.

Two earlier patent applications are assigned to the Assignee of thepresent invention and describe five chambered EDI apparatuses. One isentitled “Method of Ion Chromatography wherein a SpecializedElectrodeionization Apparatus is Used” (application Ser. No. 11/403,737)and published as US 2006/0231404. The other is entitled “ChamberedElectrodeionization Apparatus with Uniform Current Density, and Methodof Use” (application Ser. No. 11/403,734 and published as US2006/0231403). The entire contents of both applications are herebyincorporated herein by reference in their entirety.

A related patent application filed concurrently herewith and entitled“Methods and Apparatus for Electrodeionization” is assigned to theAssignee of the present invention. The entire contents of thisapplication are hereby incorporated herein by reference in its entirety.

The types of ion exchange materials that are typically of the mostinterest for the deionizations described herein are strong acid cationexchange materials and strong base anion exchange materials. The strongacid cation exchange material advantageously has a sulfonate-type ionexchange site (or functional group) while the anion exchange materialtypically has a quaternary amine ion exchange site (or functionalgroup). There are different types of cation and anion exchange materialswhich are not inherently excluded from use in connection with thedeionizations described herein, but one type of cation exchange materialand one type of anion exchange material as described are typically foundto provide adequate performance in practice and are generally used.

If the anion material and cation material are mixed in the desired ratioof substantially equal cation and anion exchange capacities, this isreferred to as a “mixed” bed. This comports with the conventionalunderstanding of a “mixed bed ion exchange material” as an ion exchangematerial that has approximately equal anion and cation exchange capacitywith one type of anion material and one type of cation material. This istypically achieved by mixing a cation exchange material (typically acation exchange resin) with an anion exchange material (typically ananion exchange resin) in a ratio such that the cation and anion exchangecapacities of the final mixture are roughly equal. In practice, it isusually not feasible to achieve precise equality but commonly the range,of anion capacity in the mixed bed can be about 40%-60% with theremaining capacity as cation capacity.

The “composite bed” concept as used herein relates to a composite as amixture of a cation and an anion exchange material without reference tothe proportions of each. That is, in a composite bed the ion exchangecapacity ratio could range from about 1% to about 99% of either materialand the balance comprising the opposite material type. Generally, threetypes of composite beds are considered:

-   -   1. A “mixed bed” where the ratio of anion to cation capacity is        approximately 1:1 with a range of about 10% (that is, 40%-60% of        either cation or anion capacity).    -   2. A “doped” anion bed where the anion capacity is at least        about 60% and the remaining capacity is cation.    -   3. A “doped” cation bed where the cation capacity is at least        about 60% and the remaining capacity is anion.

Simply put, as the proportion of cation exchange material P_(c) in a“composite bed” is increased from about 1% to about 99% we encounterfirst the particular type of composite bed called a “doped anion bed”for P_(c) less than about 40%. A “mixed bed” is produced for P_(c)greater than about 40% and less than about 60%, and a “doped cation bed”for P_(c) greater than about 60%.

The EDI apparatus shown in FIG. 1 is an example of an EDI apparatus,which comprises five discreet membrane bound chambers in electricalcommunication (although other embodiments can have more than fivechambers). The apparatus illustrated in FIG. 1 comprises an anodechamber 101 separated from an ADC 103 by a first AM 102. The anodechamber 101 includes an anode therein that typically is in electricalcontact with the first AM 102. The ADC 103 typically includes therein ahomogeneous volume of anion exchange material. A composite bed depletionchamber (or simply CBDC) 105 may be placed on the cathode-side of theADC 103. The ADC 103 and the CBDC 105 may be separated by a second AM104. The CBDC 105 may include therein a mixed ion exchange material, ora doped anion exchange material, or a doped cation exchange material.The doped anion exchange material, or doped cation exchange materialversions may be advantageous in that they can be used to improve theconductivity through the EDI apparatus and improve the performance ofthe EDI apparatus. A CDC 107 may be placed on the cathode-side of theCBDC 105. The CBDC 105 and the CDC 107 may be separated by a first CM106. The CDC 107 typically includes therein a homogeneous volume ofcation exchange material. The CDC 107 may be separated from the cathodechamber 109 by a second CM 108. The cathode chamber 109 includes acathode therein that is advantageously in electrical contact with thesecond CM 108. When additional (more than five) membrane bound chambersare present, they may be typically present in pairs of additionalhomogeneous anion and cation depletion chambers, which may be added nextto existing like chambers, which are present between an electrode andthe CBDC 105. An electrical current runs through the EDI apparatustransverse to the membranes, conventionally from left to right for theapparatus depicted in FIG. 1 as the direction of flow of positivecharges.

Each CDC may be bounded by two cation exchange membranes and may containa volume of homogeneous cation exchange material. The cation exchangematerial may comprise cation exchange resins, cation exchange particles,cation exchange fibers, cation exchange screens, cation exchangemonoliths, and combinations thereof. Typically, the cation exchangematerial may be a volume of homogeneous cation exchange resin.

The CBDC may be bounded by a cation exchange membrane from a CDC and ananion exchange membrane from an ADC, and the chamber may contain a mixedion exchange material, or a doped anion exchange material, or a dopedcation exchange material. The ion exchange material may comprise ionexchange resins, ion exchange particles, ion exchange fibers, ionexchange screens, ion exchange monoliths, and combinations thereof.

Each ADC may be bounded by two anion exchange membranes and may containa volume of homogeneous anion exchange material. The anion exchangematerial may comprise anion exchange resins, anion exchange particles,anion exchange fibers, anion exchange screens, anion exchange monoliths,and combinations thereof. Typically, the anion exchange material may bea volume of homogeneous anion exchange resin.

The ion exchange membranes used in the CEDI apparatuses to practice someembodiments of the present invention work by passive transfer and notreactive chemistry. They may contain functional sites, which allow forthe exchange of ions. The transfer of ions through the ion exchangemembrane is based upon the charge of the ion. The ion exchange membranesmay readily admit small ions but resist the passage of bulk liquid forexample. Ion exchange membranes may be anion exchange membranes (AM) orcation exchange membranes (CM), wherein they are selective to anions orcations respectively. An AM may transport anions through the membrane,but the membrane prevents the bulk flow of liquid from one side of themembrane to the other. A CM may transport cations through the membrane,but the membrane prevents the bulk flow of liquid from one side of themembrane to the other. A property common to both types of membranes isthat they must be conductive so that ions may migrate through the ionexchange membrane towards their respective electrodes.

An example of an anion exchange membrane is a microporous copolymer ofstyrene and divinylbenzene that has been chloromethylated and then thependant —CH₂Cl groups that were introduced to the aromatic rings werethen quaternized with a tertiary amine R₁R₂R₃N where R₁, R₂, and R₃represent organic groups and may represent different organic groups ormay represent the same organic group. This results in a membrane whichmay be a strong base anion exchanger. In some cases, the anion exchangemembrane may also contain a binder polymer or an inert fabric. Anexample of an anion exchange membrane that may be used in connectionwith some embodiments of the present invention is the AMI-7000S membrane(Membranes International, Glen Rock, N.J.). Other anion exchangemembranes which provide a strong base anion exchanger may also be used.

An example of a cation exchange membrane is a microporous copolymer ofstyrene and divinylbenzene that has undergone sulfonation, resulting inthe monosubstitution of —SO₃H groups on the aromatic rings of thecopolymer. This results in a membrane which may be a strong acid cationexchanger. In some cases, the cation exchange membrane may also containa binder polymer or an inert fabric. An example of a cation exchangemembrane that may be used in connection with some embodiments of thepresent invention is the CMI-7000S membrane (Membranes International,Glen Rock, N.J.). Other cation exchange membranes which provide a strongacid cation exchanger may also be used.

The ion exchange materials used in the EDI apparatuses of the kind usedto practice some embodiments of the present invention may containfunctional sites, which allow for the exchange of ions. The interactionbetween ions and the ion exchange materials is based upon the charge ofthe ion. The ion exchange materials may readily admit small ions andmolecules but resist the intrusion of species of even a few hundredatomic mass units. Ion exchange materials may be anion exchangematerials or cation exchange materials, wherein they are selective toanions or cations respectively.

An example of an anion exchange resin is a microporous copolymer ofstyrene and divinylbenzene that has been chloromethylated and then thependant —CH₂Cl groups that were introduced to the aromatic rings werethen quaternized with a tertiary amine R₁R₂R₃N where R₁, R₂, and R₃represent organic groups and may represent different organic groups ormay represent the same organic group. This results in a resin which maybe a strong base anion exchanger. There are several commerciallyavailable resins of this type. One example of an anion exchange resinthat may be used is the Dowex 1x4 resin (Dow Chemical Company, Midland,Mich.), which contains 4% divinylbenzene and is in the ionic form Cl⁻.Other anion exchange resins which provide a strong base anion exchangermay also be used.

An example of a cation exchange resin is a microporous copolymer ofstyrene and divinylbenzene that has undergone sulfonation, resulting inthe monosubstitution of —SO₃H groups on the aromatic rings of thecopolymer. This results in a resin which may be a strong acid cationexchanger. There are several commercially available resins of this type.One example of a cation exchange resin that may be used is the Dowex50Wx4 resin (Dow Chemical Company, Midland, Mich.), which contains 4%divinylbenzene and is in the ionic form H⁺. Other cation exchange resinswhich provide a strong acid cation exchanger may also be used.

The CBDC may serve two functions, among others. First, when an electricfield is applied, water splitting occurs wherever anion and cationexchange materials are in direct contact with one another. Watersplitting occurs where a cation and anion exchange material contact oneanother, or where a cation exchange material contacts an anion exchangemembrane, or where an anion exchange material contacts a cation exchangemembrane. Water splitting results in the production of hydroxide andhydronium, which serve to maintain the anion exchange material in thehydroxide form and the cation exchange material in the hydronium form,respectively. As well as keeping the materials of the CBDC fullyregenerated, the hydroxide and hydronium formed at the ion exchangematerial/ion exchange membrane interfaces of the CBDC serve to providehydroxide for the at least one ADC(s) and hydronium for the at least oneCDC(s).

A second function of the CBDC may be to remove from the feed water, thefew remaining (if any) anions not removed by the ADC and the fewremaining (if any) cations not removed by the CDC. Ion transport in acomposite bed ion exchange material relies on both water splitting aswell as electrophoretic migration of the ion through the material. Watersplitting may displace contaminant ions from the ion exchange material.These contaminant ions may be driven through the composite ion exchangematerial bed of the CBDC towards their respective electrode chambers.Thus, contaminant cations may be driven through the CBDC, through a CM,through the CDC(s), and through a CM, to the cathode chamber. Likewise,contaminant anions may be driven through the CBDC, through an AM,through the ADC(s), and through an AM, to the anode chamber.

Water splitting generates hydronium and hydroxide ions which may be usedto regenerate ion exchange materials. Under the force of an appliedelectric field, water splitting can occur at the junction of anion andcation exchange materials. These junctions occur in the CBDC, since thischamber contains both anion and cation exchange materials and membranes.Hydronium from the CBDC may travel through the CM to the CDC, thusregenerating the cation exchange materials found within. Likewise,hydroxide from the CBDC may travel through the AM to the ADC, thusregenerating the anion exchange materials found within.

The following discussion will describe the movement of ions through theCBDC. For this discussion, it will be assumed that the CBDC is filledwith ion exchange particles. An example of such ion exchange particlesincludes ion exchange resins. For a contaminant ion to be removed fromthe CBDC, the contaminant ion must either come in contact with therespective membrane or be retained by an ion exchange material particlein contact with a like ion exchange membrane (cation material-cationmembrane or anion material-anion membrane). An ion that is in a materialparticle and electrophoretically migrating through the material can onlymove to the next like particle (anion or cation exchange) if the twoparticles are in contact with one another, or if the contaminant ionleaves the ion exchange material particle as a result of watersplitting. Since the CBDC contains a mixture of anion and cationexchange materials, it is statistically unlikely, for the typicaldensities of ion exchange materials used in practice, that there will bea continuous path of like ion exchange material particles of anysignificant distance, thus, electrophoretic migration in the chamber isadvantageously accompanied by displacement and retention (caused bywater splitting) for efficient ion removal. This is in contrast to themechanism of ion removal in the ADC and CDC where no water splittingoccurs (since these chambers contain only one type of ion exchangematerial). In the ADC and CDC, contaminant ions may be removed byelectrophoretic migration through the ion exchange material bed to andthrough the ion exchange membrane and ultimately to the electrodechamber.

For example, chloride retained by the anion exchange material of theCBDC may be displaced by water splitting. The hydroxide ions formed fromwater splitting may displace the contaminant anions (for example Cl⁻)from the anion exchange material and the chloride goes into solutionwhere it is “paired” with hydronium ions from the water splittingreaction. The contaminant Cl⁻ (as hydrochloric acid, HCl) may now movethrough the composite ion exchange material bed where it may be retainedagain by anion exchange, where the displacement-retention mechanismscontinue to occur. Eventually, the contaminant Cl⁻ may come in contactwith an anion exchange material particle that is in contact with theanion exchange membrane, and the contaminant Cl⁻ ion may be passedthrough the AM into the ADC.

The analogous situation occurs for a cation contaminant. For example,sodium retained by the cation exchange material of the CBDC may bedisplaced by water splitting. The hydronium ions formed from watersplitting may displace the contaminant cations (for example Na⁺) fromthe cation exchange material and the cation goes into solution where itis “paired” with hydroxide ions from the water splitting reaction. Thecontaminant Na⁺ (as sodium hydroxide, NaOH) may now move through thecomposite ion exchange material bed where it may be retained again bycation exchange, where the displacement-retention mechanisms continue tooccur. Eventually, the contaminant Na⁺ may come in contact with a cationexchange material particle that is in contact with the cation exchangemembrane, and thus the contaminant Na⁺ ion may be passed through thecation membrane into the CDC.

A method for performing electrodeionization utilizing the apparatus asillustrated in FIG. 1 comprises first causing the liquid to be deionizedto flow through the CDC 107. The CDC 107 may be capable of removingcations. The CDC 107 typically includes therein cation exchangematerials and may be effective at removing the contaminant cations. Thecations may be allowed to pass through a second CM 108 and into thecathode chamber 109. The contaminant cations may be removed from thesystem in the cathode chamber 109. The cations cannot travel toward theanode because of the influence of the applied electric field. Therefore,the cations may be effectively contained in the cathode chamber 109until they are flushed from the system by the waste liquid stream thatremoves ions from the cathode chamber 109. The anions are attractedtoward the anode under the influence of the applied electric field butwill not be allowed to pass through a first CM 106 into the adjacentCBDC 105. Therefore, the anions will be retained in the liquid. Theliquid exiting the CDC 107 has a reduced level of cations relative tothe in-coming liquid stream.

Following passage through 107, the liquid is then flowed through the ADC103. The ADC 103 may be capable of effectively removing contaminantanions from the liquid stream. The anions are attracted to the anodeunder the influence of the applied electric field and may be allowed topass through a first AM 102 and into the anode chamber 101. Thecontaminant anions may be removed from the system in the anode chamber101. The cations are not allowed to pass through a second AM 104 thatdefines the cathode-side of the ADC 103. The anions cannot travel towardthe cathode because of the influence of the applied electric field.Therefore, the anions are effectively contained in the anode chamber 101until they are flushed from the system by the waste liquid stream thatremoves ions from the anode chamber 101. Any remaining cations arelargely unaffected while passing through the ADC 103. The liquid exitingthe ADC 103 may be largely free of anionic contamination.

Following passage through 103, the liquid is then flowed through theCBDC 105. The CBDC 105 may be capable of effectively removing anyremaining cations or anions from the liquid stream. The anions areattracted to the anode under the influence of the applied electric fieldand may be allowed to pass through a second AM 104 and into the ADC 103.The contaminant anions may be removed from the system in the anodechamber 101. One benefit of this configuration is that this preventsfouling and scaling of the anode chamber 101 since the anions cannotreact with cations to form insoluble scaling materials (i.e., CaCO₃,Mg(OH)₂, etc.). The anions cannot travel toward the cathode because ofthe influence of the applied electric field. Therefore, the anions maybe effectively removed in the ADC 103 or contained in the anode chamber101 until they are flushed from the system by the waste liquid streamthat removes ions from the anode chamber 101. The cations are attractedto the cathode under the influence of the applied electric field and maybe allowed to pass through a first CM 106 and into the CDC 107. Thecontaminant cations may be removed from the system in the cathodechamber 109. The cations cannot travel toward the anode because of theinfluence of the applied electric field. Therefore, the cations may beeffectively removed in the CDC 107 or contained in the cathode chamber109 until they are flushed from the system by the waste liquid streamthat removes ions from the cathode chamber 109.

Water splitting occurs in the CBDC 105 since it may include therein acomposite of anion and cation exchange materials. The water splitting inthe CBDC 105 serves to regenerate the second AM 104 that separates theCBDC 105 from the ADC 103 as well as the first CM 106 that separates theCBDC 105 from the adjacent CDC 107. Additionally, hydronium ionsgenerated by the water splitting are attracted to the cathode and enterthe adjacent CDC 107 where they may be effective in regenerating thecation exchange material contained therein. Additionally, hydroxide ionsgenerated by the water splitting are attracted to the anode and enterthe adjacent ADC 103 where they may be effective in regenerating theanion exchange material contained therein.

Example 1

An EDI device as shown in FIG. 1 was constructed using machined highdensity polyethylene hardware to retain the electrodes, membranes andion exchange resin. In this example, the device was substantiallycylindrical in shape with a substantially circular cross-section. Othershapes and cross-sections are feasible, but circular was convenient forthis example. The internal flow dimensions of the ADC 103 were 1.27 cmin diameter and 3.81 cm in length. The internal flow dimensions of theCBDC 105 were 1.27 cm in diameter and 1.27 cm in length. The internalflow dimensions of the CDC 107 were 1.27 cm in diameter and 3.81 cm inlength.

The anode chamber 101, for this example, contained platinum gauzeelectrodes (Unique Wire Weaving Inc, Hillside, N.J.). In contact withthe anode and separating the anode chamber from the ADC was an anionexchange membrane 102 (AMI-7001S, a product of Membranes International,Glen Rock, N.J.). The ADC was filled with an anion exchange resin(DOWEX™ 1X4 (200 mesh), a product of The Dow Chemical Company, Midland,Mich.). An anion membrane 104 separated the ADC from the CBDC 105. TheCBDC contained a doped anion resin bed. The doped anion resin bedconsisted of a composite of an anion exchange resin (DOWEX™ 1x4 (200mesh), a product of The Dow Chemical Company, Midland, Mich.) and acation exchange resin (DOWEX™ 50Wx4 (200 mesh), a product of The DowChemical Company, Midland, Mich.) with an ion exchange capacity ratio of3:1 anion to cation. The cation and anion exchange resins were in thehydronium and hydroxide forms, respectively. Separating the CDC 107 fromthe CBDC 105 was a cation exchange membrane 106 (CMI-7000, a product ofMembranes International, Glen Rock, N.J.). The CDC was filled with acation exchange resin (DOWEX™ 50Wx4 (200 mesh), a product of The DowChemical Company, Midland, Mich.). The CDC was separated from thecathode chamber 109 by a cation membrane 108 (CMI-7000, a product ofMembranes International, Glen Rock, N.J.). The cathode compartmentcontained platinum gauze electrodes (Unique Wire Weaving Inc, Hillside,N.J.). The cathode was in direct contact with the cation membraneseparating the CDC and cathode chamber. A pump (GP40, a product ofDionex, Sunnyvale, Calif.) was used to deliver reverse osmosis (RO)quality water (specific conductance 15.1 μS/cm, S=Siemens) at a flowrate of 2.0 mL/min to the EDI device shown in FIG. 1. A conductivitydetector (CD20, a product of Dionex, Sunnyvale, Calif.) with a flow cellwas used for the conductivity measurements. From the pump, the RO waterflow was directed to the CDC 107, then to the ADC 103, then to the CBDC105 and then to the flow-through conductivity cell. A peristaltic pump(MASTERFLEX LS, a product of the Cole-Parmer company, Vernon Hills,Ill.) was used to deliver deionized water at a flow rate of 2.0 mL/minto the anode chamber and then to the cathode chamber and then to waste.

Initially, the conductance of the water exiting the EDI device was 8.3μS/cm. Using a laboratory power supply, (E3612A, a product of Agilent,Santa Clara, Calif.) a constant current of 40 mA was applied and theinitial voltage was 42V. Gas evolution was observed immediately from theanode and cathode chambers. The initial background conductivity of theproduct water increased to 85 μS/cm and over a 1 hour period theconductivity decreased to 1.2 μS/cm. The EDI device was allowed tooperate continuously for 7 days. The data in Table 1 shows results forthe device of FIG. 1.

TABLE 1 Conductance Measurements vs. Time Conductivity Hours Voltage(μS/cm) 0.0 0.0 8.3 1 37 1.2 2 33 0.91 10 40 0.10 24 32 0.088 48 260.065 72 24 0.061 96 25 0.059 120 25 0.058 144 27 0.057 168 29 0.060

Another method (not shown) for performing electrodeionization utilizingthe apparatus as illustrated in FIG. 1 comprises first causing theliquid to be deionized to flow through the ADC 103. The ADC 103 may becapable of effectively removing contaminant anions from the liquidstream. The anions are attracted to the anode under the influence of theapplied electric field and may be allowed to pass through a first AM 102and into the anode chamber 101. The contaminant anions may be removedfrom the system in the anode chamber 101. The anions cannot traveltoward the cathode because of the influence of the applied electricfield. Therefore, the anions are effectively contained in the anodechamber 101 until they are flushed from the system by the waste liquidstream that removes ions from the anode chamber 101. Any cations arelargely unaffected while passing through the ADC 103. The liquid exitingthe ADC 103 may be largely free of anionic contamination.

Following passage through 103, the liquid is then flowed through the CDC107. The CDC 107 may be capable of removing cations. The CDC 107typically includes therein cation exchange materials and may beeffective at removing the contaminant cations. The cations may beallowed to pass through a second CM 108 and into the cathode chamber109. The contaminant cations may be removed from the system in thecathode chamber 109. The cations cannot travel toward the anode becauseof the influence of the applied electric field. Therefore, the cationsmay be effectively contained in the cathode chamber 109 until they areflushed from the system by the waste liquid stream that removes ionsfrom the cathode chamber 109. The anions are attracted toward the anodeunder the influence of the applied electric field but will not beallowed to pass through a first CM 106 into the adjacent CBDC 105.Therefore, the anions will be retained in the liquid. The liquid exitingthe CDC 107 has a reduced level of cations relative to the in-comingliquid stream.

Following passage through 107, the liquid is then flowed through theCBDC 105. The CBDC 105 may be capable of effectively removing anyremaining cations or anions from the liquid stream. The anions areattracted to the anode under the influence of the applied electric fieldand may be allowed to pass through a second AM 104 and into the ADC 103.The contaminant anions may be removed from the system in the anodechamber 101. The anions cannot travel toward the cathode because of theinfluence of the applied electric field. Therefore, the anions may beeffectively removed in the ADC 103 or contained in the anode chamber 101until they are flushed from the system by the waste liquid stream thatremoves ions from the anode chamber 101. The cations are attracted tothe cathode under the influence of the applied electric field and may beallowed to pass through a first CM 106 and into the CDC 107. Thecontaminant cations may be removed from the system in the cathodechamber 109. One benefit of this configuration is that this preventsfouling and scaling of the cathode chamber 109 since the cations cannotreact with anions to form insoluble scaling materials (i.e., CaCO₃,Mg(OH)₂, etc.). The cations cannot travel toward the anode because ofthe influence of the applied electric field. Therefore, the cations maybe effectively removed in the CDC 107 or contained in the cathodechamber 109 until they are flushed from the system by the waste liquidstream that removes ions from the cathode chamber 109.

Water splitting occurs in the CBDC 105 since it may include therein acomposite of anion and cation exchange materials. The water splitting inthe CBDC 105 serves to regenerate the second AM 104 that separates theCBDC 105 from the ADC 103 as well as the first CM 106 that separates theCBDC 105 from the adjacent CDC 107. Additionally, hydronium ionsgenerated by the water splitting are attracted to the cathode and enterthe adjacent CDC 107 where they may be effective in regenerating thecation exchange material contained therein. Additionally, hydroxide ionsgenerated by the water splitting are attracted to the anode and enterthe adjacent ADC 103 where they may be effective in regenerating theanion exchange material contained therein.

FIG. 2 illustrates one configuration of some embodiments of the presentinvention that may be used to produce liquid with very low anioncontamination and reduced cation contamination. In the apparatusillustrated in FIG. 2, a single ion depletion chamber may be layeredwith an anion exchange material layer 203 and a composite anion-cationexchange material layer 204. In contrast to the structure of FIG. 1, ina layered structure such as that of FIGS. 2-16, no membranes or otherstructures are used to separate ion exchange material layers that fillsome of the chambers lying between the anode chamber and the cathodechamber. The layers may be in contiguous contact without an ion exchangemembrane separating them. This is an example of a layered depletionchamber (LDC). Since there are two depletion layers 203, 204 between theAM 202 and the CM 205 in FIG. 2 without a membrane or other structurebetween them, this is an example of an EDI apparatus having dual iondepletion layers or, in other words, having a dual-layer depletionchamber. The interface between the anion exchange material layer 203 andthe composite anion-cation exchange material layer 204 may be transverseto the applied electric field. The anion exchange material layer 203 maybe positioned on the anode-side of the chamber and may be separated fromthe anode chamber 201 by an AM 202. The anion exchange material layer203 typically includes therein a homogeneous volume of anion exchangematerial. The composite anion-cation exchange material layer 204 may bepositioned on the cathode-side of the chamber and may be separated fromthe cathode chamber 206 by a CM 205. The composite anion-cation exchangematerial layer 204 may include therein a mixed ion exchange material, ora doped anion exchange material, or a doped cation exchange material.The anion exchange material layer 203 may serve to remove the anioniccontaminates and the composite anion-cation exchange material layer 204may serve to remove cationic contaminants as well as anioniccontaminants from the liquid. The apparatus as illustrated in FIG. 2 maybe operated in continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus asillustrated in FIG. 2 comprises first causing the liquid to be deionizedto flow through the anion exchange material layer 203. The liquid to bedeionized is caused to flow through the anion exchange material layer203 first by the placement of the input port on the apparatus. The anionexchange material layer 203 may be effective at removing anions from theliquid. The anions are attracted toward the anode by the appliedelectric field. The anions may be allowed to pass through the AM 202 andinto the anode chamber 201 where they may be removed by the waste streamused to flush the anode chamber. Cations are prevented from flowing intothe anode chamber 201 by both the AM 202 and the applied electric field.The cations are attracted toward the cathode and may enter the compositeanion-cation exchange material layer 204 directly. The cations may beallowed to pass through the CM 205 and into the cathode chamber 206where they may be removed by the waste stream used to flush the cathodechamber. Anions are prevented from flowing into the cathode chamber 206by both the CM 205 and the applied electric field.

Following the passage through 203, the liquid is then flowed through thecomposite anion-cation exchange material layer 204 where most of thecations may be removed and any remaining anions may be removed. Theliquid is caused to flow through the composite anion-cation exchangematerial layer 204 by the placement of the output port on the apparatus.The liquid exits the apparatus as product liquid having a reduced levelof anions and cations. Since this apparatus may be particularlyconfigured for anion removal, the volume of the anion exchange materialwill typically be in the range from about 50% to about 90% of the totalion exchange material volume within the chamber. The apparatus andmethod as illustrated in FIG. 2 may result in an apparatus that mayprovide a product liquid stream with reduced levels of anioniccontamination.

The apparatus as illustrated in FIG. 2 may be suitable for deionization,especially anion removal, for low ionic strength liquids. Examples oflow ionic strength liquids include water that has received reverseosmosis, distillation, or prior deionization treatment among others. Theapparatus as illustrated in FIG. 2 may produce a liquid with very lowconcentrations of anions and may be used for purifying liquids for usein analytical techniques such as ion chromatography, inductively coupledplasma mass spectrometry, and atomic absorption spectroscopy, amongothers.

FIG. 3 illustrates one configuration of the present invention that maybe used to produce liquid with very low cation contamination and reducedanion contamination. In the apparatus illustrated in FIG. 3, a singleion depletion chamber is layered with a cation exchange material layer304 and a composite anion-cation exchange material layer 303. This is anexample of a layered depletion chamber (LDC), in this example, a duallayer LDC. The layers may be in contiguous contact without an ionexchange membrane separating them. The interface between the compositeanion-cation exchange material layer 303 and the cation exchangematerial layer 304 may be transverse to the applied electric field. Thecomposite anion-cation exchange material layer 303 may be positioned onthe anode-side of the chamber and may be separated from the anodechamber 301 by an AM 302. The composite anion-cation exchange materiallayer 303 may include therein a mixed ion exchange material, or a dopedanion exchange material, or a doped cation exchange material. The cationexchange material layer 304 may be positioned on the cathode-side of thechamber and may be separated from the cathode chamber 306 by a CM 305.The cation exchange material layer 304 typically includes therein ahomogeneous volume of cation exchange material. The cation exchangematerial layer 304 may serve to remove the cationic contaminates and thecomposite anion-cation exchange material layer 303 may serve to removeanionic contaminants as well as cationic contaminants from the liquid.The apparatus as illustrated in 3 may be operated in continuous mode orin intermittent mode.

A method for performing electrodeionization utilizing the apparatus asillustrated in FIG. 3 comprises first causing the liquid to be deionizedto flow through the cation exchange material layer 304. The liquid iscaused to flow through the cation exchange material layer 304 first bythe placement of the input port on the apparatus. The cation exchangematerial layer 304 may be effective at removing cations from the liquid.The cations are attracted toward the cathode by the applied electricfield. The cations may be allowed to pass through the CM 305 and intothe cathode chamber 306 where they may be removed by the waste streamused to flush the cathode chamber 306. Anions are prevented from flowinginto the cathode chamber 306 by both the CM 305 and the applied electricfield. The anions are attracted toward the anode and may enter theanion-cation exchange material layer 303 directly. The anions may beallowed to pass through the AM 302 and into the anode chamber 301 wherethey may be removed by the waste stream used to flush the anode chamber301. Cations are prevented from flowing into the anode chamber 301 byboth the AM 302 and the applied electric field.

Following the passage through 304, the liquid is then caused to flowthrough the composite anion-cation exchange material layer 303 wheremost of the anions may be removed and any remaining cations may beremoved. The liquid is next caused to flow through the compositeanion-cation exchange material layer 303 by the placement of the outputport on the apparatus. The liquid exits the apparatus as product liquidhaving a reduced level of anions and cations. Since this apparatus maybe particularly configured for cation removal, the volume of the cationexchange material will typically be in the range from about 50% to about90% of the total ion exchange material volume within the chamber. Theapparatus and method as illustrated in FIG. 3 result in an apparatusthat may provide a product liquid stream with much reduced levels ofcationic contamination.

The apparatus as illustrated in FIG. 3 may be suitable for deionization,especially cation removal, for low ionic strength liquids. Examples oflow ionic strength liquids may comprise water that has received reverseosmosis, distillation, or prior deionization treatment. The apparatus asillustrated in FIG. 3 may produce a liquid with very low concentrationsof cations and may be used for purifying liquids for use in analyticaltechniques such as ion chromatography, inductively coupled plasma massspectrometry, and atomic absorption spectroscopy, among others.

Example 2

The device of FIG. 3 was constructed using machined high densitypolyethylene hardware to retain the electrodes, membranes and resin. TheLDC was 1.27 cm in diameter and 3.81 cm in length. The liquid flow inletwas directed to the top of the cation resin layer 304 close to theinterface between the cation resin 304 and the CM 305. The cation resinlayer 304 was approximately 3 cm in length. The liquid flow exited atthe composite or doped anion-cation resin layer 303 at the interface ofthe anion-cation resin layer 303 and the AM 302. The composite or dopedanion-cation resin layer 303 was approximately 0.8 cm in length.

The anode chamber 301, for this example, contained platinum gauzeelectrodes (Unique Wire Weaving Inc, Hillside, N.J.). In contact withthe anode and separating the anode chamber 301 from the LDC was an AM302 (AMI-7001, a product of Membranes International, Glen Rock, N.J.).The LDC in this example consisted of two layers 303 and 304 in FIG. 3.One layer is a composite resin layer 303 (the composite layer was doped,2:1 cation to anion capacity) comprising a composite of an anionexchange resin 303 (Dowex 1x4 (200 mesh), a product of The Dow ChemicalCompany, Midland, Mich.) and a cation exchange resin (DOWEX™ 50Wx4 (200mesh), a product of The Dow Chemical Company, Midland, Mich.). Thesecond layer is a cation exchange resin layer 304 (DOWEX™ 50Wx4 (200mesh), a product of The Dow Chemical Company, Midland, Mich.). Thecation and anion exchange resins were in the hydronium and hydroxideforms, respectively. A cation exchange membrane 305 (CMI-7000, a productof Membranes International, Glen Rock, N.J.) separated the LDC from thecathode chamber 306. The cathode chamber 306 contained platinum gauzeelectrodes (Unique Wire Weaving Inc, Hillside, N.J.). The cathode was indirect contact with the CM 305 separating the LDC and cathode chamber306. A pump (GP40, a product of Dionex, Sunnyvale, Calif.) was used todeliver reverse osmosis (RO) quality water (specific conductance 11.2μS/cm) at a flow rate of 2.0 mL/min to the EDI device shown in FIG. 3. Aconductivity detector (CD20, a product of Dionex, Sunnyvale, Calif.)with a flow cell was used for the conductivity measurements. From thepump, the RO water flow was directed to the cation resin layer 304 ofthe LDC and exited at the anion-cation resin layer 303 to theconductivity cell. From the conductivity cell, the flow was directed tothe anode chamber 301 and then the cathode chamber 306 and finally towaste.

Initially, the conductance of the water exiting the EDI device was 2.6μS/cm. Using a laboratory power supply, (E3612A, a product of Agilent,Santa Clara, Calif.) a constant current of 40 mA was applied and theinitial voltage was 23V. Gas evolution was observed immediately from theanode and cathode chambers. The initial background conductivity of theproduct water increased to 53 μS/cm and over a 1 hour period theconductivity decreased to 1.1 μS/cm. The EDI device was allowed tooperate continuously for 6 days. The data in Table 2 shows results forthe device of FIG. 3.

TABLE 2 Conductance Measurements vs. Time Conductivity Hours Voltage(μS/cm) 0.0 0.0 2.6 1 20 1.1 2 33 0.87 10 40 0.36 24 32 0.11 48 26 0.07872 24 0.064 96 25 0.060 120 25 0.058 144 27 0.061

Another embodiment of the present invention is illustrated in FIG. 4Aand FIG. 4B. This embodiment illustrates an apparatus which comprises acomposite anion-cation material layer 404 that may be disposed betweenan anion exchange material layer 403 and a cation exchange materiallayer 405. This is another example of an LDC, in this example, a triplelayer LDC. The anion exchange material layer 403 includes therein anionexchange material. The cation exchange material layer 405 includestherein cation exchange material. The composite anion-cation materiallayer 404 includes therein a mixed ion exchange material, or a dopedanion exchange material, or a doped cation exchange material. In thisapparatus, the liquid to be deionized may be caused to flow in eitherdirection depending upon the liquid quality required. The anion exchangematerial layer 403 may be separated from the anode chamber 401 by an AM402. The cation exchange material layer 405 may be separated from thecathode chamber 407 by a CM 406. The anion exchange material layer 403,composite anion-cation material layer 404, and cation exchange materiallayer 405 may be contiguous with one another without separation by ionexchange membranes. The interface between the composite anion-cationexchange material layer 404 and the cation exchange material layer 405may be transverse to the applied electric field. The interface betweenthe composite anion-cation exchange material layer 404 and the anionexchange material layer 403 may be transverse to the applied electricfield. The apparatus as illustrated in FIG. 4A and FIG. 4B may beoperated in continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated in FIG. 4A. If the requirement is for a product liquid lowin anionic contamination, the liquid may be initially directed throughthe cation exchange material layer 405. The cation exchange materiallayer 405 may remove most of the cations from the liquid. The cationswill be attracted toward the cathode by the applied electric field. Thecations may be allowed to pass through the CM 406 and into the cathodechamber 407 where they may be removed by the waste stream used to flushthe cathode chamber 407. Anions will be attracted toward the anode bythe applied electric field. The anions may continue to pass through thecomposite anion-cation exchange material layer 404, through the anionexchange layer 403, through the AM 402 and into the anode chamber 401where they may be removed from the system.

Following its passage through layer 405, the liquid may then passthrough the composite anion-cation exchange material layer 404 whereboth anions and cations may be removed from the liquid. The cations willbe attracted toward the cathode by the applied electric field. Thecations may pass through the cation exchange material layer 405, throughthe CM 406 and into the cathode chamber 407 where they may be removedfrom the system. The anions will be attracted toward the anode by theapplied electric field. The anions may pass through the anion exchangematerial layer 403, through the AM 402 and into the anode chamber 401where they may be removed from the system.

Following its passage through layer 404, the liquid may then passthrough the anion exchange material layer 403. The anion exchangematerial layer 403 may remove most of the remaining anions from theliquid. The anions will be attracted toward the anode by the appliedelectric field. The anions may be allowed to pass through the AM 402 andinto the anode chamber 401 where they may be removed by the waste streamused to flush the anode chamber 401. Remaining cations will be attractedtoward the cathode by the applied electric field. Some of the remainingcations may continue to pass through the composite anion-cation exchangematerial layer 404, through the cation exchange layer 405, through theCM 406 and into the cathode chamber 407 where they may be removed fromthe system. The apparatus illustrated in FIG. 4A may produce liquid witha reduced concentration of anions, but may contain trace amines orammonium from degradation of the anion exchange material.

The homogeneous anion exchange material layer 403 and homogeneous cationexchange material layer 405 illustrated in FIG. 4A may be regenerated bywater splitting that occurs within the composite anion-cation exchangematerial layer 404. Hydronium ions will be attracted toward the cathodeby the applied electric field and may regenerate the homogeneous cationexchange material layer 405 as they travel toward the cathode. Hydroxideions will be attracted toward the anode by the applied electric fieldand may regenerate the homogeneous anion exchange material layer 403 asthey travel toward the anode.

The apparatus as illustrated in FIG. 4A may be suitable fordeionization, especially anion removal, for low ionic strength liquids.Examples of low ionic strength liquids include water that has receivedreverse osmosis, distillation, or prior deionization treatment, amongothers. The apparatus as illustrated in FIG. 4A may produce a liquidwith very low concentrations of anions and may be used for purifyingliquids for use in analytical techniques such as ion chromatography,inductively coupled plasma mass spectrometry, and atomic absorptionspectroscopy, among others.

Another method for performing electrodeionization utilizing thisapparatus is illustrated in FIG. 4B. If the requirement is for a productliquid low in cationic contamination, the liquid may be initiallydirected through the anion exchange material layer 403. The anionexchange material layer 403 may remove most of the anions from theliquid. The anions will be attracted toward the anode by the appliedelectric field. The anions may be allowed to pass through the AM 402 andinto the anode chamber 401 where they may be removed by the waste streamused to flush the anode chamber 401. Cations will be attracted towardthe cathode by the applied electric field. The cations may continue topass through the composite anion-cation exchange material layer 404,through the cation exchange layer 405, through the CM 406 and into thecathode chamber 407 where they may be removed from the system.

Following passage through 403, the liquid may then pass through thecomposite anion-cation exchange material layer 404 where both anions andcations may be removed from the liquid. The cations will be attractedtoward the cathode by the applied electric field. The cations may passthrough the cation exchange material layer 405, through the CM 406 andinto the cathode chamber 407 where they may be removed from the system.The anions will be attracted toward the anode by the applied electricfield. The anions may pass through the anion exchange material layer403, through the AM 402 and into the anode chamber 401 where they may beremoved from the system.

Following passage through 404, the liquid may then pass through thecation exchange material layer 405. The cation exchange material layer405 may remove most of the remaining cations from the liquid. Thecations will be attracted toward the cathode by the applied electricfield. The cations may be allowed to pass through the CM 406 and intothe cathode chamber 407 where they may be removed by the waste streamused to flush the cathode chamber 407. Remaining anions will beattracted toward the anode by the applied electric field. Some of theremaining anions may continue to pass through the composite anion-cationexchange material layer 404, through the anion exchange layer 403,through the AM 402 and into the anode chamber 401 where they may beremoved from the system. The apparatus illustrated in FIG. 4B mayproduce liquid with a reduced concentration of contaminant cations, butmay contain trace amounts of sulfate from degradation of the cationresin bed.

The homogeneous anion exchange material layer 403 and homogeneous cationexchange material layer 405 illustrated in FIG. 4B may be regenerated bywater splitting that occurs within the composite anion-cation exchangematerial layer 404. Hydronium ions will be attracted toward the cathodeby the applied electric field and may regenerate the homogeneous cationexchange material layer 405 as they travel toward the cathode. Hydroxideions will be attracted toward the anode by the applied electric fieldand may regenerate the homogeneous anion exchange material layer 403 asthey travel toward the anode.

The apparatus as illustrated in FIG. 4B may be suitable fordeionization, especially cation removal, for low ionic strength liquids.Examples of low ionic strength liquids include water that has receivedreverse osmosis, distillation, or prior deionization treatment, amongothers. The apparatus as illustrated in FIG. 4B may produce a liquidwith very low concentrations of cations and may be used for purifyingliquids for use in analytical techniques such as ion chromatography,inductively coupled plasma mass spectrometry, and atomic absorptionspectroscopy, among others.

Another embodiment of the present invention is illustrated in FIG. 5A.Similar to the apparatus illustrated in FIG. 4A, this embodimentillustrates an apparatus which contains a first composite anion-cationmaterial layer 504 that may be disposed between an anion exchangematerial layer 503 and a cation exchange material layer 505. The anionexchange material layer 503 typically includes therein a homogeneousvolume of anion exchange material. The cation exchange material layer505 typically includes therein a homogeneous volume of cation exchangematerial. The first composite anion-cation exchange material layer 504may include therein a mixed ion exchange material, or a doped anionexchange material, or a doped cation exchange material. However, thisembodiment comprises an additional, second, composite anion-cationmaterial layer 506 between the cation exchange material layer 505 andthe cathode chamber 508. This is another example of a LDC, in theexample, a quad layer LDC. The second composite anion-cation exchangematerial layer 506 may include therein a mixed ion exchange material, ora doped anion exchange material, or a doped cation exchange material.The second composite anion-cation exchange material layer 506 may beseparated from the cathode chamber 508 by a CM 507. The anion exchangematerial layer 503 may be separated from the anode chamber 501 by an AM502. The anion exchange material layer 503, first composite anion-cationexchange material layer 504, cation exchange material layer 505, andsecond composite anion-cation material layer 506, are contiguous withone another without separation by ion exchange membranes. The interfacebetween the anion exchange material layer 503 and the first compositeanion-cation exchange material layer 504 may be transverse to theapplied electric field. The interface between the first compositeanion-cation exchange material layer 504 and the cation exchangematerial layer 505 may be transverse to the applied electric field. Theinterface between the cation exchange material layer 505 and the secondcomposite anion-cation exchange material layer 506 may be transverse tothe applied electric field. The apparatus as illustrated in FIG. 5A maybe operated in continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated by the dashed flow path in FIG. 5A. The liquid may beinitially directed through the anion exchange material layer 503. Theanion exchange material layer may remove most of the anions from theliquid. The anions will be attracted toward the anode by the appliedelectric field. The anions may be allowed to pass through the AM 502 andinto the anode chamber 501 where they may be removed by the waste streamused to flush the anode chamber 501. Cations will be attracted towardthe cathode by the applied electric field. The cations may continue topass through the first composite anion-cation exchange material layer504, through the cation exchange layer 505, through the second compositeanion-cation exchange material layer 506, through the CM 507 and intothe cathode chamber 508 where they may be removed from the system.

Following passage through 503, the liquid may then pass through thefirst composite anion-cation exchange material layer 504 where bothanions and cations may be removed from the liquid. The cations will beattracted toward the cathode by the applied electric field. The cationsmay pass through the cation exchange material layer 505, through thesecond composite anion-cation exchange material layer 506, through theCM 507 and into the cathode chamber 508 where they may be removed fromthe system. The anions will be attracted toward the anode by the appliedelectric field. The anions may pass through the anion exchange materiallayer 503, through the AM 502 and into the anode chamber 501 where theymay be removed from the system.

Following passage through 504, the liquid may then pass through thecation exchange material layer 505. The cation exchange material layer505 may remove most of the remaining cations from the liquid. Thecations will be attracted toward the cathode by the applied electricfield. The cations may be allowed to pass through the second compositeanion-cation exchange material layer 506, through the CM 507 and intothe cathode chamber 508 where they may be removed by the waste streamused to flush the anode chamber. Anions will be attracted toward theanode by the applied electric field. The anions may continue to passthrough the first composite anion-cation exchange material layer 504,through the anion exchange layer 503, through the AM 502 and into theanode chamber 501 where they may be removed from the system.

Following passage through 505, the liquid may then pass through thesecond composite anion-cation exchange material layer 506. The secondcomposite anion-cation exchange material layer 506 may remove most ofthe remaining cations from the liquid. The cations will be attractedtoward the cathode by the applied electric field. The cations may beallowed to pass through the CM 507 and into the cathode chamber 508where they may be removed by the waste stream used to flush the cathodechamber 508. Any remaining anions may be retained in the product liquid.

Another method for performing electrodeionization utilizing theapparatus is illustrated by the solid flow path in FIG. 5A. In thiscase, the liquid may pass first through the second compositeanion-cation exchange material layer 506. The second compositeanion-cation exchange material layer 506 may remove anions and cationsfrom the liquid. The cations will be attracted toward the cathode by theapplied electric field. The cations may be allowed to pass through theCM 507 and into the cathode chamber 508 where they may be removed by thewaste stream used to flush the cathode chamber 508. Anions may beattracted toward the anode by the applied electric field. The anions maycontinue to pass through the cation exchange material layer 505, throughthe first composite anion-cation exchange material layer 504, throughthe anion exchange layer 503, through the AM 502 and into the anodechamber 501 where they may be removed from the system.

Following passage through 506, the liquid may then pass through thecation exchange material layer 505. The cation exchange material layer505 may remove most of the remaining cations from the liquid. Thecations will be attracted toward the cathode by the applied electricfield. The cations may be allowed to pass through the second compositeanion-cation exchange material layer 506, through the CM 507 and intothe cathode chamber 508 where they may be removed by the waste streamused to flush the cathode chamber 508. Anions will be attracted towardthe anode by the applied electric field. The anions may continue to passthrough the first composite anion-cation exchange material layer 504,through the anion exchange layer 503, through the AM 502 and into theanode chamber 501 where they may be removed from the system.

Following passage through 505, the liquid may then pass through thefirst composite anion-cation exchange material layer 504 where bothanions and cations may be removed from the liquid. The anions will beattracted toward the anode by the applied electric field. The anions maypass through the anion exchange material layer 503, through the AM 502and into the anode chamber 501 where they may be removed from thesystem. The cations will be attracted toward the cathode by the appliedelectric field. The cations may pass through the cation exchangematerial layer 505, through the second anion-cation exchange materiallayer 506, through the CM 507 and into the cathode chamber 508 wherethey may be removed from the system.

Following passage through 504, the liquid may be finally directedthrough the anion exchange material layer 503. The anion exchangematerial layer may remove most of the remaining anions from the liquid.The anions will be attracted toward the anode by the applied electricfield. The anions may be allowed to pass through the AM 502 and into theanode chamber 501 where they may be removed by the waste stream used toflush the anode chamber 501. Any remaining cations may be retained inthe product liquid.

The apparatus illustrated in FIG. 5A may produce liquid with a reducedconcentration of all ions, but may contain trace sulfate ions from thedegradation of the cation exchange material layer.

The anion exchange material layer 503, cation exchange material layer505, AM 502, and CM 507 illustrated in FIG. 5A may be regenerated bywater splitting that occurs within the first composite anion-cationexchange material layer 504 and second composite anion-cation exchangematerial layers 506. Hydronium ions will be attracted toward the cathodeby the applied electric field and may regenerate the homogeneous cationexchange material layer 505 and CM 507 as they travel toward thecathode. Hydroxide ions will be attracted toward the anode by theapplied electric field and may regenerate the homogeneous anion exchangematerial layer 503 and AM 502 as they travel toward the anode.

The apparatus as illustrated in FIG. 5A may be suitable fordeionization, especially anion removal, for low ionic strength liquids.Examples of low ionic strength liquids include water that has receivedreverse osmosis, distillation, or prior deionization treatment, amongothers. The apparatus as illustrated in FIG. 5A may produce a liquidwith very low concentrations of anions and may be used for purifyingliquids for use in analytical techniques such as ion chromatography,inductively coupled plasma mass spectrometry, and atomic absorptionspectroscopy, among others.

Another embodiment of the present invention is illustrated in FIG. 5B.Similar to the apparatus illustrated in FIG. 4B, this embodimentillustrates an apparatus which contains a second composite anion-cationmaterial layer 515 that may be disposed between a cation exchangematerial layer 516 and an anion exchange material layer 514. However,this embodiment comprises an additional first composite anion-cationmaterial layer 513 between the anion exchange material layer 514 and theanode chamber 511. This is another example of a LDC, in the example, aquad layer LDC. The anion exchange material layer 514 typically includestherein a homogeneous volume of anion exchange material. The cationexchange material layer 516 typically includes therein a homogeneousvolume of cation exchange material. The first composite anion-cationexchange material layer 513 may include therein a mixed ion exchangematerial, or a doped anion exchange material, or a doped cation exchangematerial. The second composite anion-cation exchange material layer 515may include therein a mixed ion exchange material, or a doped anionexchange material, or a doped cation exchange material. The firstcomposite anion-cation exchange material layer 513 may be separated fromthe anode chamber 511 by an AM 512. The cation exchange material layer516 may be separated from the cathode chamber 518 by a CM 517. The firstcomposite anion-cation exchange material layer 513, anion exchangematerial layer 514, second composite anion-cation material layer 515,and cation exchange material layer 516, may be contiguous with oneanother without separation by ion exchange membranes. The interfacebetween the first composite anion-cation exchange material layer 513 andthe anion exchange material layer 514 may be transverse to the appliedelectric field. The interface between the anion exchange material layer514 and the second composite anion-cation exchange material layer 515may be transverse to the applied electric field. The interface betweenthe second composite anion-cation exchange material layer 515 and thecation exchange material layer 516 may be transverse to the appliedelectric field. The apparatus as illustrated in FIG. 5B may be operatedin continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated by the dashed flow path in FIG. 5B. The liquid may beinitially directed through the cation exchange material layer 516. Thecation exchange material layer 516 may remove most of the cations fromthe liquid. The cations will be attracted toward the cathode by theapplied electric field. The cations may be allowed to pass through theCM 517 and into the cathode chamber 518 where they may be removed by thewaste stream used to flush the cathode chamber 518. Anions will beattracted toward the anode by the applied electric field. The anions maycontinue to pass through the second composite anion-cation exchangematerial layer 515, through the anion exchange layer 514, through thefirst composite anion-cation exchange material layer 513, through the AM512 and into the anode chamber 511 where they may be removed from thesystem.

Following passage through 516, the liquid may then pass through thesecond composite anion-cation exchange material layer 515 where bothanions and cations may be removed from the liquid. The anions will beattracted toward the anode by the applied electric field. The anions maypass through the anion exchange material layer 514, through the firstcomposite anion-cation exchange material layer 513, through the AM 512and into the anode chamber 511 where they may be removed from thesystem. The cations will be attracted toward the cathode by the appliedelectric field. The cations may pass through the cation exchangematerial layer 516, through the CM 517 and into the cathode chamber 518where they may be removed from the system.

Following passage through 515, the liquid may then pass through theanion exchange material layer 514. The anion exchange material layer mayremove most of the remaining anions from the liquid. The anions will beattracted toward the anode by the applied electric field. The anions maybe allowed to pass through the first anion-cation exchange materiallayer 513, through the AM 512 and into the anode chamber 511 where theymay be removed by the waste stream used to flush the anode chamber 511.Cations will be attracted toward the cathode by the applied electricfield. The cations may continue to pass through the second compositeanion-cation exchange material layer 515, through the cation exchangelayer 516, through the CM 517 and into the cathode chamber 518 wherethey may be removed from the system.

Following passage through 514, the liquid may then pass through thefirst composite anion-cation exchange material layer 513 where bothanions and cations may be removed from the liquid. The anions will beattracted toward the anode by the applied electric field. The anions maypass through the AM 512 and into the anode chamber 511 where they may beremoved from the system. Any remaining cations may be retained in theproduct liquid.

Another method for performing electrodeionization utilizing theapparatus is illustrated by the solid flow path in FIG. 5B. In thiscase, the liquid may first pass through the first composite anion-cationexchange material layer 513 where both anions and cations may be removedfrom the liquid. The anions will be attracted toward the anode by theapplied electric field. The anions may pass through the AM 512 and intothe anode chamber 511 where they may be removed from the system. Cationswill be attracted toward the cathode by the applied electric field.Cations may pass through the anion exchange material layer 514, throughthe second composite anion-cation exchange material layer 515, throughthe cation exchange material layer 516, through the CM 517 and into thecathode chamber 518 where they may be removed from the system.

Following passage through 513, the liquid may then pass through theanion exchange material layer 514. The anion exchange material layer 514may remove most of the remaining anions from the liquid. The anions willbe attracted toward the anode by the applied electric field. The anionsmay be allowed to pass through the first anion-cation exchange materiallayer 513, through the AM 512 and into the anode chamber 511 where theymay be removed by the waste stream used to flush the anode chamber 511.Cations will be attracted toward the cathode by the applied electricfield. The cations may continue to pass through the second compositeanion-cation exchange material layer 515, through the cation exchangelayer 516, through the CM 517 and into the cathode chamber 518 wherethey may be removed from the system.

Following passage through 514, the liquid may then pass through thesecond composite anion-cation exchange material layer 515 where bothanions and cations may be removed from the liquid. The anions will beattracted toward the anode by the applied electric field. The anions maypass through the anion exchange material layer 514, through the firstcomposite anion-cation exchange material layer 513, through the AM 512and into the anode chamber 511 where they may be removed from thesystem. The cations will be attracted toward the cathode by the appliedelectric field. The cations may pass through the cation exchangematerial layer 516, through the CM 517 and into the cathode chamber 518where they may be removed from the system.

Following passage through 515, the liquid may be finally directedthrough the cation exchange material layer 516. The cation exchangematerial layer 516 may remove most of the remaining cations from theliquid. The cations will be attracted toward the cathode by the appliedelectric field. The cations may be allowed to pass through the CM 517and into the cathode chamber 518 where they may be removed by the wastestream used to flush the cathode chamber 518. Any remaining anions maybe retained in the product liquid.

The apparatus illustrated in FIG. 5B may produce liquid with a reducedconcentration of all ions, but may contain trace cations (in the flowdirection 516 to 513 and trace anions in the flow direction 513 to 516).

The homogeneous anion exchange material layer 514, homogeneous cationexchange material layer 516, AM 512 and CM 517 illustrated in FIG. 5Bmay be regenerated by water splitting that occurs within the firstcomposite anion-cation exchange material layer 513 and second compositeanion-cation exchange material layer 515. Hydronium ions will beattracted toward the cathode by the applied electric field and mayregenerate the homogeneous cation exchange material layer 516 and CM 517as they travel toward the cathode. Hydroxide ions will be attractedtoward the anode by the applied electric field and may regenerate thehomogeneous anion exchange material layer 514 and AM 512 as they traveltoward the anode.

The apparatus as illustrated in FIG. 5B is thus capable of being used ina manner that renders it suitable for deionization, especially cationremoval, for low ionic strength liquids. Examples of low ionic strengthliquids include water that has received reverse osmosis, distillation,or prior deionization treatment. The apparatus as illustrated in FIG. 5Bis thus capable of producing a liquid with very low concentrations ofcations and thus may be suitable for purifying liquids for use inanalytical techniques such as ion chromatography, inductively coupledplasma mass spectrometry, and atomic absorption spectroscopy, amongothers.

Another embodiment of the present invention is illustrated in FIG. 6.The apparatus illustrated in FIG. 6 comprises an anode chamber 601including an anode therein. A dual layer depletion chamber may be placedon the cathode side of the anode chamber. The layers 603, 604 may be incontiguous contact without an ion exchange membrane separating them.This is an example of a LDC, in this example, a dual layer LDC. Theanode chamber 601 and the dual layer depletion chamber may be separatedby an AM 602. The dual layer depletion chamber may be comprised of ananion exchange material layer 603 on the anode side of the chamber and acomposite anion-cation exchange material layer 604 on the cathode sideof the chamber. The anion exchange material layer 603 of the dual layerdepletion chamber typically includes therein a homogeneous volume ofanion exchange material. The anion exchange material layer 603 of thedual layer depletion chamber and the composite anion-cation exchangematerial layer 604 of the dual layer depletion chamber may be incontact. The interface between the composite anion-cation exchangematerial layer 604 of the dual layer depletion chamber and the anionexchange material layer 603 of the dual layer depletion chamber may betransverse to the applied electric field. The composite anion-cationexchange material layer 604 of the dual layer depletion chamber mayinclude therein a mixed ion exchange material, or a doped anion exchangematerial, or a doped cation exchange material. A CDC 606 may be placedon the cathode-side of the dual-layer chamber. The CDC 606 and thedual-layer chamber may be separated by a first CM 605. The CDC 606typically includes therein a homogeneous volume of cation exchangematerial. The CDC 606 may be separated from a cathode chamber 608 by asecond CM 607. The cathode chamber 608 includes a cathode therein. Theapparatus as illustrated in FIG. 6 may be operated in continuous mode orin intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated in FIG. 6. The liquid may be initially directed through theCDC 606. The CDC 606 may remove most of the cations from the liquid. Thecations will be attracted toward the cathode by the applied electricfield. The cations may be allowed to pass through the second CM 607 andinto the cathode chamber 608 where they may be removed by the wastestream used to flush the cathode chamber 608. The anions will beattracted toward the anode by the applied electric field. The anions maybe retained in the liquid since they will be prevented from passingthrough the first CM 605.

Following passage through 606, the liquid then flows through the duallayer depletion chamber. The liquid is caused to flow through the anionexchange material layer 603 first by the placement of the input port onthe apparatus. The anion exchange material layer 603 may be effective atremoving anions from the liquid. The anions are attracted toward theanode by the applied electric field. The anions may be allowed to passthrough the AM 602 and into the anode chamber 601 where they may beremoved by the waste stream used to flush the anode chamber 601. Thecations are attracted toward the cathode and enter the compositeanion-cation exchange material layer 604 directly. The cations may beallowed to pass through the composite anion-cation exchange materiallayer 604, through the first CM 605, through the CDC 606, through thesecond CM 607, and into the cathode chamber 608 where they may beremoved by the waste stream used to flush the cathode chamber 608.

Following its passage through 603, the liquid is then flowed through thecomposite anion-cation exchange material layer 604 where any remainingcations may be removed and any remaining anions may be removed. Anyremaining anions will be attracted toward the anode. The anions may passthrough the anion exchange material layer 603, through the AM 602, andinto the anode chamber 601 where they may be removed by the waste streamused to flush the anode chamber 601. Any remaining cations may beallowed to pass through the 20, first CM 605, through the CDC 606,through the second CM 607, and into the cathode chamber 608 where theymay be removed by the waste stream used to flush the cathode chamber608. The liquid is caused to flow through the composite anion-cationexchange material layer 604 last by the placement of the output port onthe apparatus. The liquid exits the apparatus as product liquid having areduced level of anions and cations.

The apparatus as illustrated in FIG. 6 is thus capable of being used ina manner that renders it suitable for deionization, especially anionremoval, for low ionic strength liquids. Examples of low ionic strengthliquids include water that has received reverse osmosis, distillation,or prior deionization treatment. The apparatus as illustrated in FIG. 6is thus capable of producing a liquid with very low concentrations ofanions and thus may be suitable for purifying liquids for use inanalytical techniques such as ion chromatography, inductively coupledplasma mass spectrometry, and atomic absorption spectroscopy, amongothers.

Example 3

An EDI device as shown in FIG. 6 was constructed using machined highdensity polyethylene hardware to retain the electrodes, membranes andresin. The internal flow dimensions of the CDC 606 were 1.27 cm indiameter and 1.27 cm in length. The internal flow dimensions of the LDCwere 1.27 cm in diameter and 3.81 cm in length.

The anode chamber 601 contained platinum gauze electrodes (Unique WireWeaving Inc, Hillside, N.J.). In contact with the anode and separatingthe anode chamber 601 from the LDC was an anion exchange membrane 602(AMI-7001, a product of Membranes International, Glen Rock, N.J.). TheLDC contained a 3 cm layer of an anion exchange resin 603 (DOWEX™ 1x4(200 mesh), a product of The Dow Chemical Company, Midland, Mich.) inthe hydroxide forms and a 0.8 cm layer of a doped cation exchange resin604 comprising cation resin (DOWEX™ 50Wx4 (200 mesh), a product of TheDow Chemical Company, Midland, Mich.) doped with an anion exchange resin(DOWEX™ 1x4 (200 mesh) a product of The Dow Chemical Company, Midland,Mich.). The doped cation resin layer 604 had an equivalence ratio of3:1, cation to anion resin. Separating the LDC from the CDC 606 was a CM605 (CMI-7000, a product of Membranes International, Glen Rock, N.J.).The CDC 606 was filled with a cation exchange resin (DOWEX™ 50Wx4 (200mesh), a product of The Dow Chemical Company, Midland, Mich.) in thehydronium form. Separating the CDC 606 from the cathode chamber 608 wasa cation exchange membrane 607 (CMI-7000, a product of MembranesInternational, Glen Rock, N.J.). A pump (GP40, a product of Dionex,Sunnyvale, Calif.) was used to deliver RO quality water (specificconductance 12.0 μS/cm) at a flow rate of 2.0 mL/min to the EDI deviceshown in FIG. 6. A conductivity detector (CD20, a product of Dionex,Sunnyvale, Calif.) with a flow cell was used for the conductivitymeasurements. From the pump, the RO water flow was directed to the CDC606, then to the inlet of the LDC. The inlet of the LDC directed thewater flow first through the anion exchange resin layer 603 and theninto the doped cation exchange resin layer 604 and finally to the flowthrough conductivity cell. From the conductivity cell, the flow wasdirected to the anode chamber 601 and then the cathode chamber 608 andfinally to waste.

Initially, the conductance of the water exiting the EDI device of FIG. 6was 5.9 μS/cm. Using a laboratory power supply, (E3612A, a product ofAgilent, Santa Clara, Calif.) a constant current of 40 mA was appliedand the initial voltage was 31V. Gas evolution was observed immediatelyfrom the anode and cathode chambers. The initial background conductivityof the product water increased to 44 gS/cm and over a 1 hour period theconductivity decreased to 0.86 μS/cm. The EDI device was allowed tooperate continuously for 5 days. The data in Table 5 shows results forthe device of FIG. 6.

TABLE 3 Conductance Measurements vs. Time Conductivity Hours voltage(μS/cm) 0.0 0.0 5.9 1 28 0.86 2 25 0.63 10 22 0.23 24 19 0.098 48 190.073 72 22 0.071 96 23 0.066 120 24 0.057

The product water from the device of FIG. 6 was analyzed by ionchromatography. The product water was directed to the sample valve of anion chromatograph (ICS-2000, a product of Dionex, Sunnyvale, Calif.)that was configured for anion analysis. A peristaltic pump (MASTERFLEXLS, a product of the Cole-Parmer company, Vernon Hills, Ill.) was usedto deliver deionized water at a flow rate of 2.0 mL/min to the anodechamber and then to the cathode chamber and then to waste. The volume ofproduct water sampled for anion analysis was 10.0 mL. The data in Table4 shows the EDI device removed all the anions to a level of 5 ng/L(parts-per-trillion) or less.

TABLE 4 Anion Concentrations of product water Ion Concentration IonRecovered (μg/L) Fluoride <0.005 Chloride <0.002 Nitrite <0.005 Bromide<0.005 Nitrate <0.005 Sulfate <0.002 Phosphate <0.002

Another embodiment of the present invention is illustrated in FIG. 7.The apparatus illustrated in FIG. 7 comprises an anode chamber 701including an anode therein. An ADC 703 may be placed on the cathode-sideof the anode chamber 701. The ADC 703 and the anode chamber 701 may beseparated by a first AM 702. The ADC 703 typically includes therein ahomogeneous volume of anion exchange material. A dual layer depletionchamber may be placed on the cathode side of the ADC 703. The ADC 703and the dual layer depletion chamber may be separated by a second AM704. The dual layer depletion chamber may be comprised of a compositeanion-cation exchange material layer 705 on the anode side of thechamber and a cation exchange material layer 706 on the cathode side ofthe chamber. This is an example of an LDC. The cation exchange materiallayer 706 of the dual layer depletion chamber and the compositeanion-cation exchange material layer 705 of the dual layer depletionchamber may be in contiguous contact. The interface between thecomposite anion-cation exchange material layer 705 of the dual layerdepletion chamber and the cation exchange material layer 706 of the duallayer depletion chamber may be transverse to the applied electric field.The composite anion-cation exchange material layer 705 of the dual layerdepletion chamber may include therein a mixed ion exchange material, ora doped anion exchange material, or a doped cation exchange material.The cation exchange material layer 706 of the dual layer depletionchamber typically includes therein a homogeneous volume of cationexchange material. The dual layer depletion chamber may be separatedfrom a cathode chamber 708 by a CM 707. The cathode chamber 708 includesa cathode therein. The apparatus as illustrated in FIG. 7 may beoperated in continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated by the flow path in FIG. 7. The liquid to be deionized maybe initially directed through the ADC 703. The ADC 703 may remove mostof the anions from the liquid. The anions will be attracted toward theanode by the applied electric field. The anions may be allowed to passthrough the first AM 702 and into the anode chamber 701 where they maybe removed by the waste stream used to flush the anode chamber 701. Thecations will be attracted toward the cathode by the applied electricfield. The cations may be retained in the liquid since they will beprevented from passing through the second AM 704 that forms thecathode-side of the ADC 703 chamber.

Following passage through 703, the liquid then flows through the duallayer depletion chamber. The liquid is caused to flow through the cationexchange material layer 706 first by the placement of the input port onthe apparatus. The cation exchange material layer 706 may be effectiveat removing cations from the liquid. The cations are attracted towardthe cathode by the applied electric field. The cations may be allowed topass through the CM 707 and into the cathode chamber 708 where they maybe removed by the waste stream used to flush the cathode chamber 708.The anions are attracted toward the anode and enter the compositeanion-cation exchange material layer 705 directly. The anions may beallowed to pass through the composite anion-cation exchange materiallayer 705, through the second AM 704, through the ADC 703, through thefirst AM 702, and into the anode chamber 701 where they may be removedby the waste stream used to flush the anode chamber 701.

Following passage through 706, the liquid is then flowed through thecomposite anion-cation exchange material layer 705 where any remainingcations may be removed and any remaining anions may be removed. Anyremaining cations will be attracted toward the cathode. The cations maypass through the cation exchange material layer 706, through the CM 707,and into the cathode chamber 708 where they may be removed by the wastestream used to flush the cathode chamber 708. Any remaining anions maybe allowed to pass through the second AM 704, through the ADC 703,through the first AM 702, and into the anode chamber 701 where they maybe removed by the waste stream used to flush the anode chamber 701. Theliquid is caused to flow through the composite anion-cation exchangematerial layer 705 last by the placement of the output port on theapparatus. The liquid exits the apparatus as product liquid having areduced level of anions and cations.

The apparatus as illustrated in FIG. 7 is thus capable of being used ina manner that renders it suitable for deionization, especially cationremoval, for low ionic strength liquids. Examples of low ionic strengthliquids include water that has received reverse osmosis, distillation,or prior deionization treatment. The apparatus as illustrated in FIG. 7is thus capable of producing a liquid with very low concentrations ofcations and thus may be suitable for purifying liquids for use inanalytical techniques such as ion chromatography, inductively coupledplasma mass spectrometry, and atomic absorption spectroscopy, amongothers.

In the apparatuses described in connection with FIGS. 2-7, thecontaminant ions may be drawn into the electrode chambers and thenremoved by the waste stream used to flush the electrode chambers. Twoconfigurations in which the contaminant ions are drawn into a CBCCinstead of the electrode chambers are illustrated in FIG. 8 and FIG. 9.

FIG. 8 illustrates an EDI apparatus comprising two ion depletionchambers, a CBCC 805, an anode chamber 801, and a cathode chamber 810.The two electrode chambers, 801, 810, and the CBCC 805, have flows ofwaste stream liquid passing through them (not depicted in FIG. 8) andused to flush the contaminant ions from the chambers. The apparatusillustrated in FIG. 8 comprises an anode chamber 801 including an anodetherein. A CDC 803 may be placed on the cathode-side of the anodechamber 801. The CDC 803 and the anode chamber 801 may be separated by afirst CM 802. The CDC 803 typically includes therein a homogeneousvolume of cation exchange material. A CBCC 805 may be placed on thecathode side of the CDC 803. The CDC 803 and the CBCC 805 may beseparated by a second CM 804. The CBCC 805 may include therein a mixedion exchange material, or a doped anion exchange material, or a dopedcation exchange material. A dual layer depletion chamber may be placedon the cathode side of the CBCC 805. The layers 807, 808, may be incontiguous contact without an ion exchange membrane separating them.This is an example of an LDC. The CBCC 805 and the dual layer depletionchamber may be separated by an AM 806. The dual layer depletion chambermay be comprised of an anion exchange material layer 807 on the anodeside of the chamber and composite anion-cation exchange material layer808 on the cathode side of the chamber. The anion exchange materiallayer 807 of the dual layer depletion chamber and the compositeanion-cation exchange material layer 808 of the dual layer depletionchamber are in contiguous contact. The interface between the compositeanion-cation exchange material layer 808 of the dual layer depletionchamber and the anion exchange material layer 807 of the dual layerdepletion chamber may be transverse to the applied electric field. Theanion exchange material layer 807 of the dual layer depletion chambertypically includes therein a homogeneous volume of anion exchangematerial. The composite anion-cation exchange material layer 808 of thedual layer depletion chamber may include therein a mixed ion exchangematerial, or a doped anion exchange material, or a doped cation exchangematerial. The dual layer depletion chamber may be separated from acathode chamber 810 by a third CM 809. The cathode chamber 810 includesa cathode therein. The apparatus as illustrated in FIG. 8 may beoperated in continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated in FIG. 8. The liquid may be initially directed through theCDC 803. The CDC 803 may remove most of the cations from the liquid. Theliquid may be caused to enter the CDC 803 close to the second CM 804 dueto the placement of the input to the CDC 803. The cations will beattracted toward the cathode by the applied electric field. The cationsmay be allowed to pass through the second CM 804 and into the CBCC 805where they may be removed by the waste stream used to flush the CBCC 805chamber. Since the liquid stream enters the chamber close to the secondCM 804, the removal efficiency of the cations may be enhanced.Additionally, the outlet of the CDC 803 may be configured to be close tothe first CM 802. This configuration may serve to maximize theinteraction length and interaction time of the liquid with the cationexchange material in the CDC 803. This may further increase the removalefficiency of the cations. The anions will be attracted toward the anodeby the applied electric field. The anions may be retained in the liquidsince they will be prevented from passing through the first CM 802 thatforms the anode-side of the CDC 803 chamber.

Following passage through 803, the liquid then flows through the duallayer depletion chamber. The liquid is caused to flow through the anionexchange material layer 807 first by the placement of the input port onthe apparatus to be close to the AM 806. The anion exchange materiallayer 807 may be effective at removing anions from the liquid. Theanions are attracted toward the anode by the applied electric field. Theanions may be allowed to pass through the AM 806 and into the CBCC 805where they may be removed by the waste stream used to flush the CBCC805. Remaining cations are attracted toward the cathode and enter thecomposite anion-cation exchange material layer 808 directly. The cationsmay be allowed to pass through the composite anion-cation exchangematerial layer 808, through the third CM 809, and into the cathodechamber 810 where they may be removed by the waste stream used to flushthe cathode chamber 810.

Following passage through 807, the liquid is then flowed through thecomposite anion-cation exchange material layer 808 where any remainingcations may be removed and any remaining anions may be removed. Anyremaining anions will be attracted toward the anode. The anions may passthrough the anion exchange material layer 807, through the AM 806, andinto the CBCC 805 where they may be removed by the waste stream used toflush the CBCC 805. Any remaining cations may be allowed to pass throughthe third CM 809 and into the cathode chamber 810 where they may beremoved by the waste stream used to flush the cathode chamber 810. Theliquid is caused to flow through the composite anion-cation exchangematerial layer 808 by the placement of the output port on the apparatus.The liquid exits the apparatus as product liquid having a reduced levelof anions and cations.

The apparatus as illustrated in FIG. 8 is thus capable of being used ina manner that renders it suitable for deionization, especially anionremoval, for low ionic strength liquids. Examples of low ionic strengthliquids include water that has received reverse osmosis, distillation,or prior deionization treatment. The apparatus as illustrated in FIG. 8is thus capable of producing a liquid with very low concentrations ofanions and thus may be suitable for purifying liquids for use inanalytical techniques such as, ion chromatography, inductively coupledplasma mass spectrometry, and atomic absorption spectroscopy, amongothers. The apparatus as illustrated in FIG. 8 has the added advantagein that the majority of the ions may be removed in a CBCC and thereforeexhibits reduced electrode fouling as discussed previously.

Example 4

An EDI device as shown in FIG. 8 was constructed using machined highdensity polyethylene hardware to retain the electrodes, membranes andresin. The internal flow dimensions of the CDC 803 were 1.27 cm indiameter and 3.81 cm in length. The internal flow dimensions of the LDCwere 1.27 cm in diameter and 3.81 cm in length. The internal flowdimensions of the CBCC were 1.27 cm in diameter and 1.27 cm in length.

The anode chamber 801 contained platinum gauze electrodes (Unique WireWeaving Inc, Hillside, N.J.). In contact with the anode and separatingthe CDC 803 from the anode chamber 801 was a CM 802 (CMI-7000, a productof Membranes International, Glen Rock, N.J.). The CDC 803 contained acation exchange resin (DOWEX™ 50Wx4 (200 mesh), a product of The DowChemical Company, Midland, Mich.) in the hydronium form. Separating theCDC 803 from the CBDC 805 was a CM 804 (CMI-7000, a product of MembranesInternational, Glen Rock, N.J.). Separating the CBCC 805 from the LDCwas an AM 806 (AMI-7001, a product of Membranes International, GlenRock, N.J.). The LDC contained a 3 cm layer 807 of an anion exchangeresin (DOWEX™ 1x4 (200 mesh), a product of The Dow Chemical Company,Midland, Mich.) in the hydroxide form and a 0.8 cm doped cation layer808 comprised of a cation exchange resin (DOWEX™ 50Wx4 (200 mesh), aproduct of The Dow Chemical Company, Midland, Mich.) doped with an anionexchange resin (DOWEX™ 1x4 (200 mesh), a product of The Dow ChemicalCompany, Midland, Mich.). The doped cation resin layer had anequivalence ratio of 3:1 cation to anion. A CM 809 (CMI-7000, a productof Membranes International, Glen Rock, N.J.), separated the LDC from thecathode chamber 810. The cathode chamber 810 contained platinum gauzeelectrodes (Unique Wire Weaving Inc, Hillside, N.J.). The cathode is indirect contact with the CM 809 separating the LDC from the cathodechamber 810. A pump (GP40, a product of Dionex, Sunnyvale, Calif.) wasused to deliver RO quality water (specific conductance 14.7 μS/cm) at aflow rate of 2.0 mL/min to the EDI device shown in FIG. 8. Aconductivity detector (CD20, a product of Dionex, Sunnyvale, Calif.)with a flow cell was used for the conductivity measurements. From thepump, the RO water flow was directed to the CDC 803, then to the LDCwith the inlet at the anion ion exchange layer 807 and the outlet at thedoped cation ion exchange layer 808 and then to the flow throughconductivity cell. A peristaltic pump (MASTERFLEX LS, a product of theCole-Parmer company, Vernon Hills, Ill.) was used to deliver deionizedwater at a flow rate of 2.0 mL/min to the anode chamber 801 and then tothe cathode chamber 810 and then to waste.

Initially, the conductance of the water exiting the EDI device was 5.1gS/cm. Using a laboratory power supply, (E3612A, a product of Agilent,Santa Clara, Calif.) a constant current of 30 mA was applied and theinitial voltage was 35V. Gas evolution was observed immediately from theanode and cathode chambers. The initial background conductivity of theproduct water increased to 41 μS/cm and over a 1 hour period theconductivity decreased to 0.95 μS/cm. The EDI device was allowed tooperate continuously for 5 days. The data in Table 5 shows results forthe device of FIG. 8.

TABLE 5 Conductance Measurements vs. Time Conductivity Hours Voltage(μS/cm) 0.0 0.0 5.1 1 31 0.95 2 29 0.32 10 26 0.093 24 22 0.072 48 200.057 72 21 0.058 96 22 0.056 120 25 0.055

The product water from the device of FIG. 8 was analyzed by ionchromatography. The product water was directed to the sample valve of anion chromatograph (ICS-2000, a product of Dionex, Sunnyvale, Calif.)that was configured for anion analysis. A peristaltic pump (MASTERFLEXLS, a product of the Cole-Parmer company, Vernon Hills, Ill.) was usedto deliver deionized water at a flow rate of 2.0 mL/min to the anodechamber and then to the cathode chamber and then to waste. The volume ofproduct water sampled for anion analysis was 10.0 mL. The data in Table6 shows the EDI device removed all the anions to a level of 5 ng/L(parts-per-trillion) or less.

TABLE 6 Anion Concentrations of product Water Ion Concentration IonRecovered (μg/L) Fluoride <0.004 Chloride <0.002 Nitrite <0.005 Bromide<0.005 Nitrate <0.005 Sulfate <0.002 Phosphate <0.002

FIG. 9 illustrates an EDI apparatus comprising two ion depletionchambers, a CBCC, an anode chamber, and a cathode chamber. The twoelectrode chambers and the CBCC have a flow of waste stream liquid (notdepicted in FIG. 9) in order to flush the contaminant ions from thesechambers. The apparatus illustrated in FIG. 9 comprises an anode chamber901 including an anode therein. A dual layer depletion chamber may beplaced on the cathode side of the anode chamber 901. The layers 903, 904may be in contiguous contact without an ion exchange membrane separatingthem. This is an example of a LDC. The dual layer depletion chamber andthe anode chamber may be separated by a first AM 902. The dual layerdepletion chamber may be comprised of a composite anion-cation exchangematerial layer 903 on the anode side of the chamber and a cationexchange material layer 904 on the cathode side of the chamber. Thecation exchange material layer 904 of the dual layer depletion chamberand the composite anion-cation exchange material layer 903 of the duallayer depletion chamber may be in contiguous contact. The interfacebetween the composite anion-cation exchange material layer 903 of thedual layer depletion chamber and the cation exchange material layer 904of the dual layer depletion chamber may be transverse to the appliedelectric field. The composite anion-cation exchange material layer 903of the dual layer depletion chamber may include therein a mixed ionexchange material, or a doped anion exchange material, or a doped cationexchange material. The cation exchange material layer 904 of the duallayer depletion chamber typically includes therein a homogeneous volumeof cation exchange material. A CBCC 906 may be placed on the cathodeside of the dual layer depletion chamber. The dual layer depletionchamber and the CBCC 906 may be separated by a CM 905. The CBCC 906 mayinclude therein a mixed ion exchange material, or a doped anion exchangematerial, or a doped cation exchange material. An ADC 908 may be placedon the cathode-side of the CBCC 906. The CBCC 906 and the ADC 908 may beseparated by a second AM 907. The ADC 908 typically includes therein ahomogeneous volume of anion exchange material. The ADC 908 may beseparated from a cathode chamber 910 by a third AM 909. The cathodechamber 910 includes a cathode therein. The apparatus as illustrated inFIG. 9 may be operated in continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated by the solid flow path in FIG. 9. The liquid may beinitially directed through the ADC 908. The ADC 908 may remove most ofthe anions from the liquid. The liquid may be caused to enter the ADC908 close to the second AM 907 due to the placement of the input to theADC 908. The anions will be attracted toward the anode by the appliedelectric field. The anions may be allowed to pass through the second AM907 and into the CBCC 906 where they may be removed by the waste streamused to flush the CBCC 906 chamber. Since the liquid stream enters thechamber close to the second AM 907, the removal efficiency of the anionsmay be enhanced. Additionally, the outlet of the ADC 907 may beconfigured to be close to the third AM 909. This configuration may serveto increase or maximize the interaction length and interaction time ofthe liquid with the anion exchange material in the ADC 908. This mayfurther increase the removal efficiency of the anions. The cations willbe attracted toward the cathode by the applied electric field. Thecations may be retained in the liquid since they will be prevented frompassing through the third AM 909 that forms the cathode-side of the ADC908 chamber.

Following passage through 908, the liquid then flows through the duallayer depletion chamber. The liquid is caused to flow through the cationexchange material layer 904 first by the placement of the input port onthe apparatus to be close to the CM 905. The cation exchange materiallayer 904 may be effective at removing cations from the liquid. Thecations are attracted toward the cathode by the applied electric field.The cations may be allowed to pass through the CM 905 and into the CBCC906 where they may be removed by the waste stream used to flush the CBCC906. The anions are attracted toward the anode and may enter thecomposite anion-cation exchange material layer 903 directly. The anionsmay be allowed to pass through the composite anion-cation exchangematerial layer 903, through the first AM 902, and into the anode chamber901 where they may be removed by the waste stream used to flush theanode chamber 901.

Following passage through 904, the liquid then flows through thecomposite anion-cation exchange material layer 903 where any remainingcations may be removed and any remaining anions may be removed. Anyremaining cations will be attracted toward the cathode. The cations maypass through the cation exchange material layer 904, through the CM 905,and into the CBCC 906 where they may be removed by the waste stream usedto flush the CBCC 906. Any remaining anions may be allowed to passthrough the first AM 902 and into the anode chamber 901 where they maybe removed by the waste stream used to flush the anode chamber 901. Theliquid is finally caused to flow through the composite anion-cationexchange material layer 903 last by the placement of the output port onthe apparatus. The liquid exits the apparatus as product liquid having areduced level of anions and cations.

The apparatus as illustrated in FIG. 9 may be suitable for deionization,especially cation removal, for low ionic strength liquids. Examples oflow ionic strength liquids include water that has received reverseosmosis, distillation, or prior deionization treatment, among others.The apparatus as illustrated in FIG. 9 may produce a liquid with verylow concentrations of cations and may be used for purifying liquids foruse in analytical techniques such as ion chromatography, inductivelycoupled plasma mass spectrometry, and atomic absorption spectroscopy,among others. The apparatus as illustrated in FIG. 9 has the addedadvantage in that the majority of the ions may be removed in a CBCC andtherefore exhibits reduced electrode fouling as discussed previously.

Example 5

An EDI device as shown in FIG. 9 was constructed using machined highdensity polyethylene hardware to retain the electrodes, membranes andresin. The internal flow dimensions of the ADC 908 were 1.27 cm indiameter and 3.81 cm in length. The internal flow dimensions of the LDCwere 1.27 cm in diameter and 3.81 cm in length. The internal flowdimensions of the CBCC were 1.27 cm in diameter and 1.27 cm in length.

The anode chamber 901 contained platinum gauze electrodes (Unique WireWeaving Inc, Hillside, N.J.). In contact with the anode and separatingthe LDC from the anode chamber 901 was an AM 902 (AMI-7001, a product ofMembranes International, Glen Rock, N.J.). The LDC contained a 0.8 cmdoped anion exchange layer 903 comprising an anion exchange resin(DOWEX™ 1x4 (200 mesh) a product of The Dow Chemical Company, Midland,Mich.) doped with a cation exchange resin (DOWEX™ 50Wx4 (200 mesh), aproduct of The Dow Chemical Company, Midland, Mich.) and a 3 cm layer904 of a cation exchange resin (DOWEX™ 50Wx4 (200 mesh), a product ofThe Dow Chemical Company, Midland, Mich.) in the hydronium form. Thedoped anion resin layer 903 had an equivalence ratio of 3:1 anion tocation capacity. Separating the LDC from the CBCC 906 was a CM 905(CMI-7000, a product of Membranes International, Glen Rock, N.J.).Separating the CBCC 906 from the ADC 908 was an AM 907 (AMI-7001, aproduct of Membranes International, Glen Rock, N.J.). The ADC 907contained an anion exchange resign (DOWEX™ 1x4 (200 mesh) a product ofThe Dow Chemical Company, Midland, Mich.) in the hydroxide form. An AM909 (AMI-7001, a product of Membranes International, Glen Rock, N.J.)separated the ADC 908 from the cathode chamber 910. The cathode chamber910 contained platinum gauze electrodes (Unique Wire Weaving Inc,Hillside, N.J.). The cathode is in direct contact with the AM 909separating the ADC 908 from the cathode chamber 910. A pump (GP40, aproduct of Dionex, Sunnyvale, Calif.) was used to deliver RO qualitywater (specific conductance 12.7 μS/cm) at a flow rate of 2.0 mL/min tothe EDI device shown in FIG. 9. A conductivity detector (CD20, a productof Dionex, Sunnyvale, Calif.) with a flow cell was used for theconductivity measurements. From the pump, the RO water flow was directedto the ADC 908, then to the LDC with the inlet at the cation layer 904and the outlet at the doped anion layer 903 and then to the flow throughconductivity cell. A peristaltic pump (MASTERFLEX LS, a product of theCole-Parmer company, Vernon Hills, Ill.) was used to deliver deionizedwater at a flow rate of 2.0 mL/min to the anode chamber 901 and then tothe cathode chamber 910 and then to waste.

Initially, the conductance of the water exiting the EDI device was 8.2μS/cm. Using a laboratory power supply, (E3612A, a product of Agilent,Santa Clara, Calif.) a constant current of 30 mA was applied and theinitial voltage was 38V. Gas evolution was observed immediately from theanode and cathode chambers. The initial background conductivity of theproduct water increased to 63 μS/cm and over a 1 hour period theconductivity decreased to 0.63 μS/cm. The EDI device was allowed tooperate continuously for 5 days. The data in Table 7 shows results forthe device of FIG. 9.

TABLE 7 Conductance Measurements vs. Time Conductivity Hours Voltage(μS/cm) 0.0 0.0 8.2 1 32 0.63 2 28 0.10 10 26 0.081 24 23 0.074 48 190.055 72 20 0.056 96 20 0.055 120 22 0.056

The product water from the device of FIG. 9 was analyzed by ionchromatography. The product water was directed to the sample valve of anion chromatograph (ICS-2000, a product of Dionex Sunnyvale, Calif.) thatwas configured for cation analysis. A peristaltic pump (MASTERFLEX LS, aproduct of the Cole-Parmer company, Vernon Hills, Ill.) was used todeliver deionized water at a flow rate of 2.0 mL/min to the anodechamber and then to the cathode chamber and then to waste. The volume ofproduct water sampled for cation analysis was 10.0 mL. The data in Table8 shows the EDI device removed cations to a level of 2 ng/L(parts-per-trillion) or less.

TABLE 8 Cation Concentrations of product Water Ion Concentration IonRecovered (μg/L) Lithium <0.001 Ammonium <0.002 Sodium <0.001 Potassium<0.001 Calcium <0.002 Magnesium <0.002

The apparatuses in FIG. 8 and FIG. 9 may offer the advantages ofhomogenous ion exchange chambers or layers for enhanced ion removal, acomposite ion exchange layer for final polishing, and reduced build upof contaminant ions in the electrode chambers which may cause blockages,reduced liquid flow through the electrode chambers, and high electricalresistance of the apparatus.

FIG. 10 illustrates an EDI apparatus comprising three ion depletionchambers, an anode chamber, and a cathode chamber. The two electrodechambers have a flow of waste stream liquid used to flush thecontaminant ions from the chambers, not shown in FIG. 10. The apparatusillustrated in FIG. 10 comprises an anode chamber 1001 including ananode therein. An ADC 1003 may be placed on the cathode side of theanode chamber 1001. The ADC 1003 and the anode chamber 1001 may beseparated by a first AM 1002. The ADC 1003 typically includes therein ahomogeneous volume of anion exchange material. A dual layer depletionchamber may be placed on the cathode side of the ADC 1003. The duallayer depletion chamber and the ADC 1003 may be separated by a second AM1004. The dual layer depletion chamber may be comprised of a cationexchange material layer 1005 on the inlet portion of the dual layerchamber and a composite anion-cation exchange material layer 1006 on theoutlet portion of the dual layer chamber. This is an example of a LDC.The interface between the cation exchange material layer 1005 and thecomposite anion-cation exchange material layer 1006 may be parallel tothe applied electric field. The cation exchange material layer 1005typically includes therein a homogeneous volume of cation exchangematerial.

The composite anion-cation exchange material layer 1006 may includetherein a mixed ion exchange material, or a doped anion exchangematerial, or a doped cation exchange material. A CDC 1008 may be placedon the cathode side of the dual layer depletion chamber. The dual layerdepletion chamber and the CDC 1008 may be separated by a first CM 1007.The CDC 1008 typically includes therein a homogeneous volume of cationexchange material. The CDC 1008 may be separated from the cathodechamber 1010 by a second CM 1009. The cathode chamber 1010 includes acathode therein. The apparatus as illustrated in FIG. 10 may be operatedin continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated in FIG. 10. The liquid may be initially directed through theCDC 1008. The CDC 1008 may remove most of the cations from the liquid.The cations are attracted to the cathode by the applied electric field.The cations may pass through the second CM 1009 and into the cathodechamber 1010 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the cathode chamber 1010. Anionswill be attracted to the anode. The anions will be retained in theliquid because they will not pass through the first CM 1007 that formsthe anode side of the CDC 1008.

Following passage through 1008, liquid may then flow through the ADC1003. The ADC 1003 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1002 and into the anode chamber1001 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1001. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1004 that formsthe cathode side of the ADC 1003.

Following passage through 1003, the liquid may then pass through thedual layer depletion chamber. The liquid is forced to pass through thecation exchange material layer 1005 of the dual layer depletion chamberby placing the inlet portion of the chamber above the cation exchangematerial layer 1005. The cation exchange material layer 1005 may removeremaining cations from the liquid. Cations are attracted to the cathodeby the applied electric field. The cations may pass through the first CM1007, through the CDC 1008, and through the second CM 1009 and into thecathode chamber 1010 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1010. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be allowed to pass through the second AM 1004,through the ADC 1003, through the first AM 1002 and into the anodechamber 1001 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1001.

Following passage through 1005, the liquid is then passed through thecomposite anion-cation exchange material layer 1006 of the dual layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1006. The compositeanion-cation exchange material layer 1006 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1007, through the CDC 1008, and through the secondCM 1009 and into the cathode chamber 1010 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1010. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1004, through the ADC 1003, through the first AM 1002 andinto the anode chamber 1001 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1001.

Another method for performing electrodeionization utilizing theapparatus of FIG. 10 uses a different path through the apparatus (andnot depicted on FIG. 10). The liquid may be initially directed throughthe ADC 1003. The ADC 1003 may remove most of the anions from theliquid. The anions are attracted to the anode by the applied electricfield. The anions may pass through the first AM 1002 and into the anodechamber 1001 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1001. Remainingcations will be attracted to the cathode. The cations will be retainedin the liquid because they will not pass through the second AM 1004 thatforms the cathode side of the ADC 1003.

Following passage through 1003, liquid may then flow through the CDC1008. The CDC 1008 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1009 and into the cathode chamber1010 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1010. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1007 that forms theanode side of the CDC 1008.

Following passage through 1008, liquid may then pass through the duallayer depletion chamber. The liquid is forced to pass through the cationexchange material layer 1005 of the dual layer depletion chamber byplacing the inlet portion of the chamber above the cation exchangematerial layer 1005. The cation exchange material layer 1005 may removeremaining cations from the liquid. Cations are attracted to the cathodeby the applied electric field. The cations may pass through the first CM1006, through the CDC 1008, and through the second CM 1009 and into thecathode chamber 1010 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1010. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be allowed to pass through the second AM 1004,through the ADC 1003, through the first AM 1002 and into the anodechamber 1001 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1001.

The liquid is then passed through the composite anion-cation exchangematerial layer 1006 of the dual layer depletion chamber by placing theoutlet portion of the chamber below the composite anion-cation exchangematerial layer 1006. The composite anion-cation exchange material layer1006 may be effective at removing both remaining anions and cations. Theremaining cations are attracted to the cathode by the applied electricfield. The cations may pass through the first CM 1007, through the CDC1008, and through the second CM 1009 and into the cathode chamber 1010where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1010. The remaining anionsare attracted to the anode by the applied electric field. The anions maybe allowed to pass through the second AM 1004, through the ADC 1003,through the first AM 1002 and into the anode chamber 1001 where they maybe removed from the apparatus by the waste liquid stream that removesions from the anode chamber 1001.

Water splitting generates hydronium and hydroxide ions which may be usedto regenerate ion exchange materials. Under the force of an appliedelectric field, water splitting can occur at the junction of anion andcation exchange materials. These junctions occur in the compositeanion-cation exchange material layer 1006 of the dual layer depletionchamber, since this chamber contains both anion and cation exchangematerials and AM and CM membranes, 1004, 1007. Hydronium from thecomposite anion-cation exchange material layer 1006 may travel throughthe first CM 1007 to the CDC 1008, thus regenerating the cation exchangematerials found within. Likewise, hydroxide from the compositeanion-cation exchange material layer 1006 may travel through the secondAM 1004 to the ADC 1003, thus regenerating the anion exchange materialsfound within.

FIG. 11 illustrates an EDI apparatus comprising three ion depletionchambers, an anode chamber, and a cathode chamber. The two electrodechambers have a flow of waste stream liquid used to flush thecontaminant ions from the chambers, not shown in FIG. 11. The apparatusillustrated in FIG. 11 comprises an anode chamber 1101 including ananode therein. An ADC 1103 may be placed on the cathode side of theanode chamber 1101. The ADC 1103 and the anode chamber 1101 may beseparated by a first AM 1102. The ADC 1103 typically includes therein ahomogeneous volume of anion exchange material. A dual layer depletionchamber may be placed on the cathode side of the ADC 1103. The layersmay be in contiguous contact without an ion exchange membrane separatingthem. This is an example of a LDC. The dual layer depletion chamber andthe ADC 1103 may be separated by a second AM 1104. The dual layerdepletion chamber may contain an anion exchange material layer 1105 onthe inlet portion of the dual layer chamber and a composite anion-cationexchange material layer 1106 on the outlet portion of the dual layerchamber. The interface between the anion exchange material layer 1105and the composite anion-cation exchange material layer 1106 may besubstantially parallel to the applied electric field. The anion exchangematerial layer 1105 typically includes therein a homogeneous volume ofanion exchange material. The composite anion-cation exchange materiallayer 1106 may include therein a mixed ion exchange material, or a dopedanion exchange material, or a doped cation exchange material. A CDC 1108may be placed on the cathode side of the dual layer depletion chamber.The dual layer depletion chamber and the CDC 1108 may be separated by afirst CM 1107. The CDC 1108 typically includes therein a homogeneousvolume of cation exchange material. The CDC 1108 may be separated fromthe cathode chamber 1110 by a second CM 1109. The cathode chamber 1110includes a cathode therein. The apparatus as illustrated in FIG. 11 maybe operated in continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated in FIG. 11. The liquid may be initially directed through theCDC 1108. The CDC 1108 may remove most of the cations from the liquid.The cations are attracted to the cathode by the applied electric field.The cations may pass through the second CM 1109 and into the cathodechamber 1110 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the cathode chamber 1110. Anionswill be attracted to the anode. The anions will be retained in theliquid because they will not pass through the first CM 1107 that formsthe anode side of the CDC 1108.

Following passage through 1108, the liquid may then flow through the ADC1103. The ADC 1103 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1102 and into the anode chamber1101 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1101. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1104 that formsthe cathode side of the ADC 1103.

Following passage through 1103, the liquid may then pass through thedual layer depletion chamber. The liquid is passed through the anionexchange material layer 1105 of the dual layer depletion chamber byplacing the inlet portion of the chamber above the anion exchangematerial layer 1105. The anion exchange material layer 1105 may removeremaining anions from the liquid. Anions are attracted to the anode bythe applied electric field. The anions may pass through the second AM1104, through the ADC 1103, and through the first AM 1102 and into theanode chamber 1101 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the anode chamber 1101. Thecations will be attracted to the cathode by the applied electric field.Some of the cations may be allowed to pass through the first CM 1107,through the CDC 1108, through the second CM 1109 and into the cathodechamber 1110 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the cathode chamber 1110.

Following passage through 1105, the liquid is then passed through thecomposite anion-cation exchange material layer 1106 of the dual layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1106. The compositeanion-cation exchange material layer 1106 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1107, through the CDC 1108, and through the secondCM 1109 and into the cathode chamber 1110 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1110. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1104, through the ADC 1103, through the first AM 1102 andinto the anode chamber 1101 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1101.

Example 6

An EDI device as shown in FIG. 11 was constructed using machined highdensity polyethylene hardware to retain the electrodes, membranes andresin. The internal flow dimensions of the ADC 1103 were 1.27 cm indiameter and 3.81 cm in length. The internal flow dimensions of the LDCwere 1.27 cm in diameter and 1.27 cm in length. The internal flowdimensions of the CDC 1108 were 1.27 cm in diameter and 3.81 cm inlength.

The anode chamber 1101 contained platinum gauze electrodes (Unique WireWeaving Inc, Hillside, N.J.). In contact with the anode and separatingthe anode chamber 1101 from the ADC 1103 was an AM 1102 (AMI-7001, aproduct of Membranes International, Glen Rock, N.J.). The ADC 1103 wasfilled with an anion exchange (DOWEX™ 1x4 (200 mesh), a product of TheDow Chemical Company, Midland, Mich.) in the hydroxide form. An AM 1104(AMI-7001, a product of Membranes International, Glen Rock, N.J.)separated the ADC 1103 from the LDC. The LDC contained a 0.5 cm anionexchange resin layer 1105 (DOWEX™ 1x4 (200 mesh), a product of The DowChemical Company, Midland, Mich.) and a 0.8 cm composite bed layer 1106.The composite bed layer 1106 contained a composite of a cation exchangeresin (DOWEX™ 50Wx4 (200 mesh), a product of The Dow Chemical Company,Midland, Mich.) and an anion exchange resin (DOWEX™ 1x4 (200 mesh), aproduct of The Dow Chemical Company, Midland, Mich.) with an equivalenceratio of 1:1 anion to cation resin. The cation and anion exchange resinswere in the hydronium and hydroxide forms, respectively. Separating theCDC 1108 from the LDC was a CM 1107 (CMI-7000, a product of MembranesInternational, Glen Rock, N.J.). The CDC 1108 was filled with a cationexchange resin (DOWEX™ 50Wx4 (200 mesh), a product of The Dow ChemicalCompany, Midland, Mich.). The CDC 1108 was separated from the cathodechamber 1110 by a CM 1109 (CMI-7000, a product of MembranesInternational, Glen Rock, N.J.). The cathode chamber 1110 containedplatinum gauze electrodes (Unique Wire Weaving Inc, Hillside, N.J.). Thecathode was in direct contact with the CM 1109 separating the CDC 1108and the cathode chamber 1110. A pump (GP40, a product of Dionex,Sunnyvale, Calif.) was used to deliver RO quality water (specificconductance 11.7 μS/cm) at a flow rate of 2.0 mL/min to the EDI deviceshown in FIG. 11. A conductivity detector (CD20, a product of Dionex,Sunnyvale, Calif.) with a flow cell was used for the conductivitymeasurements. From the pump, the RO water flow was directed to the CDC1108, then the ADC 1103, to the anion layer 1105 inlet of the LDCthrough the composite bed layer 1106 outlet and then to the flow throughconductivity cell. A peristaltic pump (MASTERFLEX LS, a product of theCole-Parmer company, Vernon Hills, Ill.) was used to deliver deionizedwater at a flow rate of 2.0 mL/min to the anode chamber 1101 and then tothe cathode chamber 1110 and then to waste.

Initially, the conductance of the water exiting the EDI device was 2.1μS/cm. Using a laboratory power supply, (E3612A, a product of Agilent,Santa Clara, Calif.) a constant current of 40 mA was applied and theinitial voltage was 56V. Gas evolution was observed immediately from theanode and cathode chambers. The initial background conductivity of theproduct water increased to 53 μS/cm and over a 1 hour period theconductivity decreased to 0.34 μS/cm. The EDI device was allowed tooperate continuously for 7 days. The data in Table 9 shows results forthe device of FIG. 11.

TABLE 9 Conductance Measurements vs. Time Conductivity Hours Voltage(μS/cm) 0.0 0.0 2.1 1 51 0.34 2 33 0.15 10 40 0.087 24 32 0.061 48 260.056 72 24 0.055 96 25 0.055 120 25 0.056 144 27 0.055 168 29 0.056

Another method (not shown in FIG. 11) for performing electrodeionizationutilizing the apparatus as illustrated in FIG. 11 is essentially amirror-image of the flow depicted by the solid flow path in FIG. 11. Theliquid may be initially directed through the ADC 1103. The ADC 1103 mayremove most of the anions from the liquid. The anions are attracted tothe anode by the applied electric field. The anions may pass through thefirst AM 1102 and into the anode chamber 1101 where they may be removedfrom the apparatus by the waste liquid stream that removes ions from theanode chamber 1101. Remaining cations will be attracted to the cathode.The cations will be retained in the liquid because they will not passthrough the second AM 1104 that forms the cathode side of the ADC 1103.

Following passage through 1103, the liquid may then flow through the CDC1108. The CDC 1108 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1109 and into the cathode chamber1110 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1110. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1107 that forms theanode side of the CDC 1108.

Following passage through 1108, the liquid may then pass through thedual layer depletion chamber. The liquid is passed through the anionexchange material layer 1105 of the dual layer depletion chamber byplacing the inlet portion of the chamber above the anion exchangematerial layer 1105. The anion exchange material layer 1105 may removeremaining anions from the liquid. Anions are attracted to the anode bythe applied electric field. The anions may pass through the second AM1104, through the ADC 1103, and through the first AM 1102 and into theanode chamber 1101 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the anode chamber 1101. Thecations will be attracted to the cathode by the applied electric field.Some of the cations may be allowed to pass through the first CM 1107,through the CDC 1108, through the second CM 1109 and into the cathodechamber 1110 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the cathode chamber 1110.

Following passage through 1105, the liquid is then passed through thecomposite anion-cation exchange material layer 1106 of the dual layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1106. The compositeanion-cation exchange material layer 1106 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1107, through the CDC 1108, and through the secondCM 1109 and into the cathode chamber 1110 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1110. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1104, through the ADC 1103, through the first AM 1102 andinto the anode chamber 1101 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1101.

FIG. 12 illustrates an EDI apparatus comprising three ion depletionchambers, an anode chamber, and a cathode chamber. The two electrodechambers have a flow of waste stream liquid used to flush thecontaminant ions from the chambers, but not depicted in FIG. 12. Theapparatus illustrated in FIG. 12 comprises an anode chamber 1201including an anode therein. An ADC 1203 may be placed on the cathodeside of the anode chamber 1201. The ADC 1203 and the anode chamber 1201may be separated by a first AM 1202. The ADC 1203 typically includestherein a homogeneous volume of anion exchange material. A triple layerdepletion chamber may be placed on the cathode side of the ADC 1203. Thetriple layer depletion chamber and the ADC 1203 may be separated by asecond AM 1204. The triple layer depletion chamber may be comprised of acation exchange material layer 1205 on the inlet portion of the triplelayer chamber, an anion exchange material layer 1206 in the centerportion, and a composite anion-cation exchange material layer 1207 onthe outlet portion of the triple layer chamber. This is an example of aLDC. The interface between the cation exchange material layer 1205 andthe anion exchange material layer 1206 may be parallel to the appliedelectric field. The interface between the anion exchange material layer1206 and the composite anion-cation exchange material layer 1207 may beparallel to the applied electric field. The cation exchange materiallayer 1205 typically includes therein a homogeneous volume of cationexchange material. The anion exchange material layer 1206 typicallyincludes therein a homogeneous volume of anion exchange material. Thecomposite anion-cation exchange material layer 1207 may include thereina mixed ion exchange material, or a doped anion exchange material, or adoped cation exchange material. A CDC 1209 may be placed on the cathodeside of the triple layer depletion chamber. The triple layer depletionchamber and the CDC 1209 may be separated by a first CM 1208. The CDC1209 typically includes therein a homogeneous volume of cation exchangematerial. The CDC 1209 may be separated from the cathode chamber 1211 bya second CM 1210. The cathode chamber 1211 includes a cathode therein.The apparatus as illustrated in FIG. 12 may be operated in continuousmode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated in FIG. 12. The liquid may be initially directed through theCDC 1209. The CDC 1209 may remove most of the cations from the liquid.The cations are attracted to the cathode by the applied electric field.The cations may pass through the second CM 1210 and into the cathodechamber 1211 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the cathode chamber 1211. Anionswill be attracted to the anode. The anions will be retained in theliquid because they will not pass through the first CM 1208 that formsthe anode side of the CDC 1209.

Following passage through 1209, the liquid may then flow through the ADC1203. The ADC 1203 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1202 and into the anode chamber1201 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1201. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1204 that formsthe cathode side of the ADC 1203.

Following passage through 1203, the liquid may then pass through thetriple layer depletion chamber. The liquid is passed through the cationexchange material layer 1205 of the triple layer depletion chamber byplacing the inlet portion of the chamber above the cation exchangematerial layer 1205. The cation exchange material layer 1205 may removeremaining cations from the liquid. Cations are attracted to the cathodeby the applied electric field. The cations may pass through the first CM1208, through the CDC 1209, and through the second CM 1210 and into thecathode chamber 1211 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1211. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be allowed to pass through the second AM 1204,through the ADC 1203, through the first AM 1202 and into the anodechamber 1201 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1201.

Following passage through 1205, the liquid is then passed through theanion exchange material layer 1206 of the triple layer depletionchamber. The anion exchange material layer 1206 may remove remaininganions from the liquid. Anions are attracted to the anode by the appliedelectric field. The anions may pass through the second AM 1204, throughthe ADC 1203, and through the first AM 1202 and into the anode chamber1201 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1201. The cations willbe attracted to the cathode by the applied electric field. Some of thecations may be allowed to pass through the first CM 1208, through theCDC 1209, through the second CM 1210 and into the cathode chamber 1211where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1211.

Following passage through 1206, the liquid is then passed through thecomposite anion-cation exchange material layer 1207 of the triple layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1207. The compositeanion-cation exchange material layer 1207 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1208, through the CDC 1209, and through the secondCM 1210 and into the cathode chamber 1211 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1211. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1204, through the ADC 1203, through the first AM 1202 andinto the anode chamber 1201 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1201.

Another method (not shown in FIG. 12) for performing electrodeionizationutilizing the apparatus as illustrated in FIG. 12 comprises using theapparatus with essentially a mirror-image flow pattern from thatdepicted in FIG. 12. The liquid may be initially directed through theADC 1203. The ADC 1203 may remove most of the anions from the liquid.The anions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1202 and into the anode chamber1201 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1201. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1204 that formsthe cathode side of the ADC 1203.

Following passage through 1203, the liquid may then flow through the CDC1209. The CDC 1209 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1210 and into the cathode chamber1211 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1211. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1208 that forms theanode side of the CDC 1209.

Following passage through 1209, the liquid may then pass through thetriple layer depletion chamber. The liquid is passed through the cationexchange material layer 1205 of the triple layer depletion chamber byplacing the inlet portion of the chamber above the cation exchangematerial layer 1205. The cation exchange material layer 1205 may removeremaining cations from the liquid. Cations are attracted to the cathodeby the applied electric field. The cations may pass through the first CM1208, through the CDC 1209, and through the second CM 1210 and into thecathode chamber 1211 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be allowed to pass through the second AM 1204,through the ADC 1203, through the first AM 1202 and into the anodechamber 1201 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1201.

Following passage through 1205, the liquid is then passed through theanion exchange material layer 1206 of the triple layer depletionchamber. The anion exchange material layer 1206 may remove remaininganions from the liquid. Anions are attracted to the anode by the appliedelectric field. The anions may pass through the second AM 1204, throughthe ADC 1203, and through the first AM 1202 and into the anode chamber1201 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1201. The cations willbe attracted to the cathode by the applied electric field. Some of thecations may be allowed to pass through the first CM 1208, through theCDC 1209, through the second CM 1210 and into the cathode chamber 1211where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1211.

Following passage through 1206, the liquid is then passed through thecomposite anion-cation exchange material layer 1207 of the triple layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1207. The compositeanion-cation exchange material layer 1207 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1208, through the CDC 1209, and through the secondCM 1210 and into the cathode chamber 1211 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1211. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1204, through the ADC 1203, through the first AM 1202 andinto the anode chamber 1201 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1201.

FIG. 13 illustrates an EDI apparatus comprising three ion depletionchambers, an anode chamber, and a cathode chamber. The two electrodechambers have a flow of waste stream liquid used to flush thecontaminant ions from the chambers which is not depicted in FIG. 13. Theapparatus illustrated in FIG. 13 comprises an anode chamber 1301including an anode therein. An ADC 1303 may be placed on the cathodeside of the anode chamber 1301. The ADC 1303 and the anode chamber 1301may be separated by a first AM 1302. The ADC 1303 typically includestherein a homogeneous volume of anion exchange material. A dual layerdepletion chamber may be placed on the cathode side of the ADC 1303. Thedual layer depletion chamber and the ADC 1303 may be separated by asecond AM 1304. The dual layer depletion chamber may be comprised of adoped anion exchange material layer 1305 on the inlet portion of thedual layer chamber and a doped cation exchange material layer 1306 onthe outlet portion of the dual layer chamber. This is an example of aLDC. The interface between the doped anion exchange material layer 1305and the doped cation exchange material layer 1306 may be parallel to theapplied electric field. The doped anion exchange material layer 1305 mayinclude therein a composite of anion and cation exchange materialswherein the anion exchange material is responsible for at least about60% of the total ion exchange capacity and the remainder of the totalion exchange capacity is contributed by the cation exchange material.The doped cation exchange material layer 1306 may include therein acomposite of anion and cation exchange materials wherein the cationexchange material is responsible for at least about 60% of the total ionexchange capacity and the remainder of the total ion exchange capacityis contributed by anion exchange material. A CDC 1308 may be placed onthe cathode side of the dual layer depletion chamber. The dual layerdepletion chamber and the CDC 1308 may be separated by a first CM 1307.The CDC 1308 typically includes therein a homogeneous volume of cationexchange material. The CDC 1308 may be separated from the cathodechamber 1310 by a second CM 1309. The cathode chamber 1310 includes acathode therein. The apparatus as illustrated in FIG. 13 may be operatedin continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated in FIG. 13. The liquid may be initially directed through theCDC 1308. The CDC 1308 may remove most of the cations from the liquid.The cations are attracted to the cathode by the applied electric field.The cations may pass through the second CM 1309 and into the cathodechamber 1310 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the cathode chamber 1310. Anionswill be attracted to the anode. The anions will be retained in theliquid because they will not pass through the first CM 1307 that formsthe anode side of the CDC 1308.

Following passage through 1308, the liquid may then flow through the ADC1303. The ADC 1303 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1302 and into the anode chamber1301 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1301. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1304 that formsthe cathode side of the ADC 1303.

Following passage through 1303, the liquid may then pass through thedual layer depletion chamber. The liquid is passed through the dopedanion exchange material layer 1305 of the dual layer depletion chamberby placing the inlet portion of the chamber above the doped anionexchange material layer 1305. The doped anion exchange material layer1305 may remove remaining anions from the liquid. Anions are attractedto the anode by the applied electric field. The anions may pass throughthe second AM 1304, through the ADC 1303, and through the first AM 1302and into the anode chamber 1301 where they may be removed from theapparatus by the waste liquid stream that removes ions from the anodechamber 1301. The cations will be attracted to the cathode by theapplied electric field. Some of the cations may be retained by thecation ion exchange material used as a dopant and may be allowed to passthrough the first CM 1307, through the CDC 1308, through the second CM1309 and into the cathode chamber 1310 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1310.

Following passage through 1305, the liquid is then passed through thedoped cation exchange material layer 1306 of the dual layer depletionchamber by placing the outlet portion of the chamber below the cationexchange material layer 1306. The doped cation exchange material layer1306 may remove remaining cations from the liquid. Cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1307, through the CDC 1308, and through the secondCM 1309 and into the cathode chamber 1310 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1310. The anions will be attracted to the anode by theapplied electric field. Some of the anions may be retained by the anionion exchange material used as a dopant and may be allowed to passthrough the second AM 1304, through the ADC 1303, through the first AM1302 and into the anode chamber 1301 where they may be removed from theapparatus by the waste liquid stream that removes ions from the anodechamber 1301.

Another method (not shown) for performing electrodeionization utilizingthe apparatus as illustrated in FIG. 13 makes use of an alternate flowpattern. The liquid may be initially directed through the ADC 1303. TheADC 1303 may remove most of the anions from the liquid. The anions areattracted to the anode by the applied electric field. The anions maypass through the first AM 1302 and into the anode chamber 1301 wherethey may be removed from the apparatus by the waste liquid stream thatremoves ions from the anode chamber 1301. Remaining cations will beattracted to the cathode. The cations will be retained in the liquidbecause they will not pass through the second AM 1304 that forms thecathode side of the ADC 1304.

Following passage through 1303, the liquid may then flow through the CDC1308. The CDC 1308 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1309 and into the cathode chamber1310 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1310. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1307 that forms theanode side of the CDC 1308.

Following passage through 1308, the liquid may then pass through thedual layer depletion chamber. The liquid is passed through the dopedanion exchange material layer 1305 of the dual layer depletion chamberby placing the inlet portion of the chamber above the doped anionexchange material layer 1305. The doped anion exchange material layer1305 may remove remaining anions from the liquid. Anions are attractedto the anode by the applied electric field. The anions may pass throughthe second AM 1304, through the ADC 1303, and through the first AM 1302and into the anode chamber 1301 where they may be removed from theapparatus by the waste liquid stream that removes ions from the anodechamber 1301. The cations will be attracted to the cathode by theapplied electric field. Some of the cations may be retained by thecation ion exchange material used as a dopant and may be allowed to passthrough the first CM 1307, through the CDC 1308, through the second CM1309 and into the cathode chamber 1310 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1310.

Following passage through 1305, the liquid is then passed through thedoped cation exchange material layer 1306 of the dual layer depletionchamber by placing the outlet portion of the chamber below the cationexchange material layer 1306. The doped cation exchange material layer1306 may remove remaining cations from the liquid. Cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1307, through the CDC 1308, and through the secondCM 1309 and into the cathode chamber 1310 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1310. The anions will be attracted to the anode by theapplied electric field. Some of the anions may be retained by the anionion exchange material used as a dopant and may be allowed to passthrough the second AM 1304, through the ADC 1303, through the first AM1302 and into the anode chamber 1301 where they may be removed from theapparatus by the waste liquid stream that removes ions from the anodechamber 1301.

Two additional methods for performing electrodeionization (not shown) onthe apparatus as illustrated in FIG. 13 may be realized by switching theinlet and outlet of the dual layer depletion chamber. In one additionalmethod, the liquid may be initially directed through the CDC 1308. TheCDC 1308 may remove most of the cations from the liquid. The cations areattracted to the cathode by the applied electric field. The cations maypass through the second CM 1309 and into the cathode chamber 1310 wherethey may be removed from the apparatus by the waste liquid stream thatremoves ions from the cathode chamber 1310. Anions will be attracted tothe anode. The anions will be retained in the liquid because they willnot pass through the first CM 1307 that forms the anode side of the CDC1308.

Following passage through 1308, the liquid may then flow through the ADC1303. The ADC 1303 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1302 and into the anode chamber1301 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1301. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1304 that formsthe cathode side of the ADC 1303.

Following passage through 1303, the liquid may then pass through thedual layer depletion chamber. The liquid is then passed through thedoped cation exchange material layer 1306 of the dual layer depletion.The doped cation exchange material layer 1306 may remove remainingcations from the liquid. Cations are attracted to the cathode by theapplied electric field. The cations may pass through the first CM 1307,through the CDC 1308, and through the second CM 1309 and into thecathode chamber 1310 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1310. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be retained by the anion ion exchange materialused as a dopant and may be allowed to pass through the second AM 1304,through the ADC 1303, through the first AM 1302 and into the anodechamber 1301 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1301.

The liquid is passed through the doped anion exchange material layer1305 of the dual layer depletion. The doped anion exchange materiallayer 1305 may remove remaining anions from the liquid. Anions areattracted to the anode by the applied electric field. The anions maypass through the second AM 1304, through the ADC 1303, and through thefirst AM 1302 and into the anode chamber 1301 where they may be removedfrom the apparatus by the waste liquid stream that removes ions from theanode chamber 1301. The cations will be attracted to the cathode by theapplied electric field. Some of the cations may be retained by thecation ion exchange material used as a dopant and may be allowed to passthrough the first CM 1307, through the CDC 1308, through the second CM1309 and into the cathode chamber 1310 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1310.

Another additional method (not shown) for performing electrodeionizationutilizing the apparatus as illustrated in FIG. 13 makes use of analternate flow pattern. The liquid may be initially directed through theADC 1303. The ADC 1303 may remove most of the anions from the liquid.The anions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1302 and into the anode chamber1301 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1301. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1304 that formsthe cathode side of the ADC 1304.

Following passage through 1303, the liquid may then flow through the CDC1308. The CDC 1308 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1309 and into the cathode chamber1310 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1310. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1307 that forms theanode side of the CDC 1308.

Following passage through 1308, the liquid may then pass through thedual layer depletion chamber. The liquid is then passed through thedoped cation exchange material layer 1306 of the dual layer depletionchamber. The doped cation exchange material layer 1306 may removeremaining cations from the liquid. Cations are attracted to the cathodeby the applied electric field. The cations may pass through the first CM1307, through the CDC 1308, and through the second CM 1309 and into thecathode chamber 1310 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1310. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be retained by the anion ion exchange materialused as a dopant and may be allowed to pass through the second AM 1304,through the ADC 1303, through the first AM 1302 and into the anodechamber 1301 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1301.

Following passage through 1306, the liquid is passed through the dopedanion exchange material layer 1305 of the dual layer depletion chamber.The doped anion exchange material layer 1305 may remove remaining anionsfrom the liquid. Anions are attracted to the anode by the appliedelectric field. The anions may pass through the second AM 1304, throughthe ADC 1303, and through the first AM 1302 and into the anode chamber1301 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1301. The cations willbe attracted to the cathode by the applied electric field. Some of thecations may be retained by the cation ion exchange material used as adopant and may be allowed to pass through the first CM 1307, through theCDC 1308, through the second CM 1309 and into the cathode chamber 1310where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1310.

FIG. 14 illustrates an EDI apparatus comprising three ion depletionchambers, an anode chamber, and a cathode chamber. The two electrodechambers have a flow of waste stream liquid used to flush thecontaminant ions from the chambers and not depicted in FIG. 14. Theapparatus illustrated in FIG. 14 comprises an anode chamber 1401including an anode therein. An ADC 1403 may be placed on the cathodeside of the anode chamber. The ADC 1403 and the anode chamber 1401 maybe separated by a first AM 1402. The ADC 1403 typically includes thereina homogeneous volume of anion exchange material. A dual layer depletionchamber may be placed on the cathode side of the ADC 1403. The duallayer depletion chamber and the ADC 1403 may be separated by a second AM1404. The dual layer depletion chamber may be comprised of a doped anionexchange material layer 1405 on the inlet portion of the dual layerchamber and a composite anion-cation exchange material layer 1406 on theoutlet portion of the dual layer chamber. This is an example of a LDC.The interface between the doped anion exchange material layer 1405 andthe composite anion-cation exchange material layer 1406 may be parallelto the applied electric field. The doped anion exchange material layer1405 may include therein a composite of anion and cation exchangematerials wherein the anion exchange material is responsible for atleast about 60% of the total ion exchange capacity and the remainder ofthe total ion exchange capacity is contributed by the cation exchangematerial. The composite anion-cation exchange material layer 1406 mayinclude therein a mixed ion exchange material, or a doped anion exchangematerial, or a doped cation exchange material. A CDC 1408 may be placedon the cathode side of the dual layer depletion chamber. The dual layerdepletion chamber and the CDC 1408 may be separated by a first CM 1407.The CDC 1408 typically includes therein a homogeneous volume of cationexchange material. The CDC 1408 may be separated from the cathodechamber 1410 by a second CM 1409. The cathode chamber 1410 includes acathode therein. The apparatus as illustrated in FIG. 14 may be operatedin continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated in FIG. 14. The liquid may be initially directed through theCDC 1408. The CDC 1408 may remove most of the cations from the liquid.The cations are attracted to the cathode by the applied electric field.The cations may pass through the second CM 1409 and into the cathodechamber 1410 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the cathode chamber 1410. Anionswill be attracted to the anode. The anions will be retained in theliquid because they will not pass through the first CM 1407 that formsthe anode side of the CDC 1408.

Following passage through 1408, the liquid may then flow through the ADC1403. The ADC 1403 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1402 and into the anode chamber1401 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1401. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1404 that formsthe cathode side of the ADC 1403.

Following passage through 1403, the liquid may then pass through thedual layer depletion chamber. The liquid is passed through the dopedanion exchange material layer 1405 of the dual layer depletion chamberby placing the inlet portion of the chamber above the doped anionexchange material layer 1405. The doped anion exchange material layer1405 may remove remaining anions from the liquid. Anions are attractedto the anode by the applied electric field. The anions may pass throughthe second AM 1404, through the ADC 1403, and through the first AM 1402and into the anode chamber 1401 where they may be removed from theapparatus by the waste liquid stream that removes ions from the anodechamber 1401. The cations will be attracted to the cathode by theapplied electric field. Some of the cations may be retained by thecation ion exchange material used as a dopant and may be allowed to passthrough the first CM 1407, through the CDC 1408, through the second CM1409 and into the cathode chamber 1410 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1410.

Following passage through 1405, the liquid is then passed through thecomposite anion-cation exchange material layer 1406 of the dual layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1406. The compositeanion-cation exchange material layer 1406 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1407, through the CDC 1408, and through the secondCM 1409 and into the cathode chamber 1410 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1410. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1404, through the ADC 1403, through the first AM 1402 andinto the anode chamber 1401 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1401.

Another method (not shown) for performing electrodeionization utilizingthe apparatus as illustrated in FIG. 14 comprises a mirror-image flowpattern. The liquid may be initially directed through the ADC 1403. TheADC 1403 may remove most of the anions from the liquid. The anions areattracted to the anode by the applied electric field. The anions maypass through the first AM 1402 and into the anode chamber 1401 wherethey may be removed from the apparatus by the waste liquid stream thatremoves ions from the anode chamber 1401. Remaining cations will beattracted to the cathode. The cations will be retained in the liquidbecause they will not pass through the second AM 1404 that forms thecathode side of the ADC 1403.

Following passage through 1403, the liquid may then flow through the CDC1408. The CDC 1408 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1409 and into the cathode chamber1410 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1410. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1407 that forms theanode side of the CDC 1408.

Following passage through 1408, the liquid may then pass through thedual layer depletion chamber. The liquid is passed through the dopedanion exchange material layer 1405 of the dual layer depletion chamberby placing the inlet portion of the chamber above the doped anionexchange material layer 1405. The doped anion exchange material layer1405 may remove remaining anions from the liquid. Anions are attractedto the anode by the applied electric field. The anions may pass throughthe second AM 1404, through the ADC 1403, and through the first AM 1402and into the anode chamber 1401 where they may be removed from theapparatus by the waste liquid stream that removes ions from the anodechamber 1401. The cations will be attracted to the cathode by theapplied electric field. Some of the cations may be retained by thecation ion exchange material used as a dopant and may be allowed to passthrough the first CM 1407, through the CDC 1408, through the second CM1409 and into the cathode chamber 1410 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1410.

Following passage through 1405, the liquid is then passed through thecomposite anion-cation exchange material layer 1406 of the dual layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1406. The compositeanion-cation exchange material layer 1406 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1407, through the CDC 1408, and through the secondCM 1409 and into the cathode chamber 1410 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1410. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1404, through the ADC 1403, through the first AM 1402 andinto the anode chamber 1401 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1401.

Two additional methods for performing electrodeionization (not shown) onthe apparatus as illustrated in FIG. 14 may be realized by switching theinlet and outlet of the dual layer depletion chamber. In one additionalmethod, the liquid may be initially directed through the CDC 1408. TheCDC 1408 may remove most of the cations from the liquid. The cations areattracted to the cathode by the applied electric field. The cations maypass through the second CM 1409 and into the cathode chamber 1410 wherethey may be removed from the apparatus by the waste liquid stream thatremoves ions from the cathode chamber 1410. Anions will be attracted tothe anode. The anions will be retained in the liquid because they willnot pass through the first CM 1407 that forms the anode side of the CDC1408.

Following passage through 1408, the liquid may then flow through the ADC1403. The ADC 1403 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1402 and into the anode chamber1401 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1401. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1404 that formsthe cathode side of the ADC 1403.

Following passage through 1403, the liquid is then passed through thecomposite anion-cation exchange material layer 1406 of the dual layerdepletion. The composite anion-cation exchange material layer 1406 maybe effective at removing both remaining anions and cations. Theremaining cations are attracted to the cathode by the applied electricfield. The cations may pass through the first CM 1407, through the CDC1408, and through the second CM 1409 and into the cathode chamber 1410where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1410. The remaining anionsare attracted to the anode by the applied electric field. The anions maybe allowed to pass through the second AM 1404, through the ADC 1403,through the first AM 1402 and into the anode chamber 1401 where they maybe removed from the apparatus by the waste liquid stream that removesions from the anode chamber 1401.

Following passage through 1406, the liquid may then pass through thedual layer depletion chamber. The liquid is passed through the dopedanion exchange material layer 1405 of the dual layer depletion chamber.The doped anion exchange material layer 1405 may remove remaining anionsfrom the liquid. Anions are attracted to the anode by the appliedelectric field. The anions may pass, through the second AM 1404, throughthe ADC 1403, and through the first AM 1402 and into the anode chamber1401 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1401. The cations willbe attracted to the cathode by the applied electric field. Some of thecations may be retained by the cation ion exchange material used as adopant and may be allowed to pass through the first CM 1407, through theCDC 1408, through the second CM 1409 and into the cathode chamber 1410where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1410.

Another additional method (not shown) for performing electrodeionizationutilizing the apparatus as illustrated in FIG. 14 comprises an alternateflow pattern. The liquid may be initially directed through the ADC 1403.The ADC 1403 may remove most of the anions from the liquid. The anionsare attracted to the anode by the applied electric field. The anions maypass through the first AM 1402 and into the anode chamber 1401 wherethey may be removed from the apparatus by the waste liquid stream thatremoves ions from the anode chamber 1401. Remaining cations will beattracted to the cathode. The cations will be retained in the liquidbecause they will not pass through the second AM 1404 that forms thecathode side of the ADC 1403.

Following passage through 1403, the liquid may then flow through the CDC1408. The CDC 1408 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1409 and into the cathode chamber1410 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1410. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1407 that forms theanode side of the CDC 1408.

Following passage through 1408, the liquid is then passed through thecomposite anion-cation exchange material layer 1406 of the dual layerdepletion. The composite anion-cation exchange material layer 1406 maybe effective at removing both remaining anions and cations. Theremaining cations are attracted to the cathode by the applied electricfield. The cations may pass through the first CM 1407, through the CDC1408, and through the second CM 1409 and into the cathode chamber 1410where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1410. The remaining anionsare attracted to the anode by the applied electric field. The anions maybe allowed to pass through the second AM 1404, through the ADC 1403,through the first AM 1402 and into the anode chamber 1401 where they maybe removed from the apparatus by the waste liquid stream that removesions from the anode chamber 1401.

Following passage through 1406, the liquid may then pass through thedual layer depletion chamber. The liquid is passed through the dopedanion exchange material layer 1405 of the dual layer depletion chamber.The doped anion exchange material layer 1405 may remove remaining anionsfrom the liquid. Anions are attracted to the anode by the appliedelectric field. The anions may pass through the second AM 1404, throughthe ADC 1403, and through the first AM 1402 and into the anode chamber1401 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1401. The cations willbe attracted to the cathode by the applied electric field. Some of thecations may be retained by the cation ion exchange material used as adopant and may be allowed to pass through the first CM 1407, through theCDC 1408, through the second CM 1409 and into the cathode chamber 1410where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1410.

FIG. 15 illustrates an EDI apparatus comprising three ion depletionchambers, an anode chamber, and a cathode chamber. The two electrodechambers have a flow of waste stream liquid used to flush thecontaminant ions from the chambers but not depicted in FIG. 15. Theapparatus illustrated in FIG. 15 comprises an anode chamber 1501including an anode therein. An ADC 1503 may be placed on the cathodeside of the anode chamber 1501. The ADC 1503 and the anode chamber 1501may be separated by a first AM 1502. The ADC 1503 typically includestherein a homogeneous volume of anion exchange material. A dual layerdepletion chamber may be placed on the cathode side of the ADC 1503. Thedual layer depletion chamber and the ADC 1503 may be separated by asecond AM 1504. The dual layer depletion chamber may be comprised of adoped cation exchange material layer 1505 on the inlet portion of thedual layer chamber and a composite anion-cation exchange material layer1506 on the outlet portion of the dual layer chamber. This is an exampleof a LDC. The interface between the doped cation exchange material layer1505 and the composite anion-cation exchange material layer 1506 may beparallel to the applied electric field. The doped cation exchangematerial layer 1505 may include therein a composite of anion and cationexchange materials wherein the cation exchange material is responsiblefor at least about 60% of the total ion exchange capacity and theremainder of the total ion exchange capacity is contributed by anionexchange material. The composite anion-cation exchange material layer1506 may include therein a mixed ion exchange material, or a doped anionexchange material, or a doped cation exchange material. A CDC 1508 maybe placed on the cathode side of the dual layer depletion chamber. Thedual layer depletion chamber and the CDC 1508 may be separated by afirst CM 1507. The CDC 1508 typically includes therein a homogeneousvolume of cation exchange material. The CDC 1508 may be separated fromthe cathode chamber 1510 by a second CM 1509. The cathode chamber 1510includes a cathode therein. The apparatus as illustrated in FIG. 15 maybe operated in continuous mode or in intermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated in FIG. 15. The liquid may be initially directed through theCDC 1508. The CDC 1508 may remove most of the cations from the liquid.The cations are attracted to the cathode by the applied electric field.The cations may pass through the second CM 1509 and into the cathodechamber 1510 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the cathode chamber 1510. Anionswill be attracted to the anode. The anions will be retained in theliquid because they will not pass through the first CM 1507 that formsthe anode side of the CDC 1508.

Following passage through 1508, the liquid may then flow through the ADC1503. The ADC 1503 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1502 and into the anode chamber1501 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1501. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1504 that formsthe cathode side of the ADC 1503.

Following passage through 1503, the liquid may then pass through thedual layer depletion chamber. The liquid is passed through the dopedcation exchange material layer 1505 of the dual layer depletion chamberby placing the inlet portion of the chamber above the doped cationexchange material layer 1505. The doped cation exchange material layer1505 may remove remaining cations from the liquid. Cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1507, through the CDC 1508, and through the secondCM 1509 and into the cathode chamber 1510 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1510. The anions will be attracted to the anode by theapplied electric field. Some of the anions may be retained by the anionion exchange material used as a dopant and may be allowed to passthrough the second AM 1504, through the ADC 1503, through the first AM1502 and into the anode chamber 1501 where they may be removed from theapparatus by the waste liquid stream that removes ions from the anodechamber 1501.

Following passage through 1505, the liquid is then passed through thecomposite anion-cation exchange material layer 1506 of the dual layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1506. The compositeanion-cation exchange material layer 1506 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1507, through the CDC 1508, and through the secondCM 1509 and into the cathode chamber 1510 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1510. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1504, through the ADC 1503, through the first AM 1502 andinto the anode chamber 1501 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1501.

Another method (not shown) for performing electrodeionization utilizingthe apparatus as illustrated in FIG. 15 comprises a flow patternessentially the mirror image of that depicted in FIG. 15. The liquid maybe initially directed through the ADC 1503. The ADC 1503 may remove mostof the anions from the liquid. The anions are attracted to the anode bythe applied electric field. The anions may pass through the first AM1502 and into the anode chamber 1501 where they may be removed from theapparatus by the waste liquid stream that removes ions from the anodechamber 1501. Remaining cations will be attracted to the cathode. Thecations will be retained in the liquid because they will not passthrough the second AM 1504 that forms the cathode side of the ADC 1503.

Following passage through 1503, the liquid may then flow through the CDC1508. The CDC 1508 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1509 and into the cathode chamber1510 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1510. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1507 that forms theanode side of the CDC 1508.

Following passage through 1508, the liquid may then pass through thedual layer depletion chamber. The liquid is passed through the dopedcation exchange material layer 1505 of the dual layer depletion chamberby placing the inlet portion of the chamber above the doped cationexchange material layer 1505. The doped cation exchange material layer1505 may remove remaining cations from the liquid. Cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1507, through the CDC 1508, and through the secondCM 1509 and into the cathode chamber 1510 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1510. The anions will be attracted to the anode by theapplied electric field. Some of the anions may be retained by the anionion exchange material used as a dopant and may be allowed to passthrough the second AM 1504, through the ADC 1503, through the first AM1502 and into the anode chamber 1501 where they may be removed from theapparatus by the waste liquid stream that removes ions from the anodechamber 1501.

Following passage through 1505, the liquid is then passed through thecomposite anion-cation exchange material layer 1506 of the dual layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1506. The compositeanion-cation exchange material layer 1506 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1507, through the CDC 1508, and through the secondCM 1509 and into the cathode chamber 1510 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1510. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1504, through the ADC 1503, through the first AM 1502 andinto the anode chamber 1501 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1501.

Two additional methods for performing electrodeionization (not shown) onthe apparatus as illustrated in FIG. 15 may be realized by switching theinlet and outlet of the dual layer depletion chamber. In one additionalmethod, the liquid may be initially directed through the CDC 1508. TheCDC 1508 may remove most of the cations from the liquid. The cations areattracted to the cathode by the applied electric field. The cations maypass through the second CM 1509 and into the cathode chamber 1510 wherethey may be removed from the apparatus by the waste liquid stream thatremoves ions from the cathode chamber 1510. Anions will be attracted tothe anode. The anions will be retained in the liquid because they willnot pass through the first CM 1507 that forms the anode side of the CDC1508.

Following passage through 1508, the liquid may then flow through the ADC1503. The ADC 1503 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1502 and into the anode chamber1501 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1501. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1504 that formsthe cathode side of the ADC 1503.

Following passage through 1503, the liquid is then passed through thecomposite anion-cation exchange material layer 1506 of the dual layerdepletion chamber. The composite anion-cation exchange material layer1506 may be effective at removing both remaining anions and cations. Theremaining cations are attracted to the cathode by the applied electricfield. The cations may pass through the first CM 1507, through the CDC1508, and through the second CM 1509 and into the cathode chamber 1510where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1510. The remaining anionsare attracted to the anode by the applied electric field. The anions maybe allowed to pass through the second AM 1504, through the ADC 1503,through the first AM 1502 and into the anode chamber 1501 where they maybe removed from the apparatus by the waste liquid stream that removesions from the anode chamber 1501.

Following passage through 1506, the liquid may then pass through thedoped cation exchange material layer 1505 of the dual layer depletion.The doped cation exchange material layer 1505 may remove remainingcations from the liquid. Cations are attracted to the cathode by theapplied electric field. The cations may pass through the first CM 1507,through the CDC 1508, and through the second CM 1509 and into thecathode chamber 1510 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1510. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be retained by the anion ion exchange materialused as a dopant and may be allowed to pass through the second AM 1504,through the ADC 1503, through the first AM 1502 and into the anodechamber 1501 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1501.

Another additional method (not shown) for performing electrodeionizationutilizing the apparatus as illustrated in FIG. 15 comprises analternative flow pattern. The liquid may be initially directed throughthe ADC 1503. The ADC 1503 may remove most of the anions from theliquid. The anions are attracted to the anode by the applied electricfield. The anions may pass through the first AM 1502 and into the anodechamber 1501 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1501. Remainingcations will be attracted to the cathode. The cations will be retainedin the liquid because they will not pass through the second AM 1504 thatforms the cathode side of the ADC 1503.

Following passage through 1503, the liquid may then flow through the CDC1508. The CDC 1508 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1509 and into the cathode chamber1510 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1510. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1507 that forms theanode side of the CDC 1508.

Following passage through 1508, the liquid is then passed through thecomposite anion-cation exchange material layer 1506 of the dual layerdepletion chamber. The composite anion-cation exchange material layer1506 may be effective at removing both remaining anions and cations. Theremaining cations are attracted to the cathode by the applied electricfield. The cations may pass through the first CM 1507, through the CDC1508, and through the second CM 1509 and into the cathode chamber 1510where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1510. The remaining anionsare attracted to the anode by the applied electric field. The anions maybe allowed to pass through the second AM 1504, through the ADC 1503,through the first AM 1502 and into the anode chamber 1501 where they maybe removed from the apparatus by the waste liquid stream that removesions from the anode chamber 1501.

Following passage through 1506, the liquid may then pass through thedoped cation exchange material layer 1505 of the dual layer depletion.The doped cation exchange material layer 1505 may remove remainingcations from the liquid. Cations are attracted to the cathode by theapplied electric field. The cations may pass through the first CM 1507,through the CDC 1508, and through the second CM 1509 and into thecathode chamber 1510 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1510. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be retained by the anion ion exchange materialused as a dopant and may be allowed to pass through the second AM 1504,through the ADC 1503, through the first AM 1502 and into the anodechamber 1501 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1501.

FIG. 16 illustrates an EDI apparatus comprising three ion depletionchambers, an anode chamber, and a cathode chamber. The two electrodechambers have a flow of waste stream liquid used to flush thecontaminant ions from the chambers not shown in FIG. 16. The apparatusillustrated in FIG. 16 comprises an anode chamber 1601 including ananode therein. An ADC 1603 may be placed on the cathode side of theanode chamber 1601. The ADC 1603 and the anode chamber 1601 may beseparated by a first AM 1602. The ADC 1603 typically includes therein ahomogeneous volume of anion exchange material. A triple layer depletionchamber may be placed on the cathode side of the ADC 1603. The layersmay be in contiguous contact without an ion exchange membrane separatingthem. This is an example of a LDC. The triple layer depletion chamberand the ADC 1603 may be separated by a second AM 1604. The triple layerdepletion chamber may be comprised of a doped anion exchange materiallayer 1605 on the inlet portion of the dual layer chamber, a dopedcation exchange material layer 1606 in the center portion, and acomposite anion-cation exchange material layer 1607 on the outletportion of the triple layer chamber. The interface between the dopedanion exchange material layer 1605 and the doped cation exchangematerial layer 1606 may be parallel to the applied electric field. Theinterface between the doped cation exchange material layer 1606 and thecomposite anion-cation exchange material layer 1607 may be parallel tothe applied electric field. The doped anion exchange material layer 1605may include therein a composite of anion and cation exchange materialswherein the anion exchange material is responsible for at least about60% of the total ion exchange capacity and the remainder of the totalion exchange capacity is contributed by the cation exchange material.The doped cation exchange material layer 1606 may include therein acomposite of anion and cation exchange materials wherein the cationexchange material is responsible for at least about 60% of the total ionexchange capacity and the remainder of the total ion exchange capacityis contributed by anion exchange material. The composite anion-cationexchange material layer 1607 may include therein a mixed ion exchangematerial, or a doped anion exchange material, or a doped cation exchangematerial. A CDC 1609 may be placed on the cathode side of the triplelayer depletion chamber. The triple layer depletion chamber and the CDC1609 may be separated by a first CM 1608. The CDC 1609 typicallyincludes therein a homogeneous volume of cation exchange material. TheCDC 1609 may be separated from the cathode chamber 1611 by a second CM1610. The cathode chamber 1611 includes a cathode therein. The apparatusas illustrated in FIG. 16 may be operated in continuous mode or inintermittent mode.

A method for performing electrodeionization utilizing the apparatus isillustrated in FIG. 16. The liquid may be initially directed through theCDC 1609. The CDC 1609 may remove most of the cations from the liquid.The cations are attracted to the cathode by the applied electric field.The cations may pass through the second CM 1610 and into the cathodechamber 1611 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the cathode chamber 1611. Anionswill be attracted to the anode. The anions will be retained in theliquid because they will not pass through the first CM 1608 that formsthe anode side of the CDC 1609.

Following passage through 1609, the liquid may then flow through the ADC1603. The ADC 1603 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1602 and into the anode chamber1601 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1601. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1604 that formsthe cathode side of the ADC 1603.

Following passage through 1603, the liquid may then pass through thetriple layer depletion chamber. The liquid is passed through the dopedanion exchange material layer 1605 of the triple layer depletion chamberby placing the inlet portion of the chamber above the doped anionexchange material layer 1605. The doped anion exchange material layer1605 may remove remaining anions from the liquid. Anions are attractedto the anode by the applied electric field. The anions may pass throughthe second AM 1604, through the ADC 1603, and through the first AM 1602and into the anode chamber 1601 where they may be removed from theapparatus by the waste liquid stream that removes ions from the anodechamber 1601. The cations will be attracted to the cathode by theapplied electric field. Some of the cations may be retained by thecation ion exchange material used as a dopant and may be allowed to passthrough the first CM 1608, through the CDC 1609, through the second CM1610 and into the cathode chamber 1611 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1611.

Following passage through 1605, the liquid is then passed through thedoped cation exchange material layer 1606 of the triple layer depletionchamber. The doped cation exchange material layer 1606 may removeremaining cations from the liquid. Cations are attracted to the cathodeby the applied electric field. The cations may pass through the first CM1608, through the CDC 1609, and through the second CM 1610 and into thecathode chamber 1611 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1611. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be retained by the anion ion exchange materialused as a dopant and may be allowed to pass through the second AM 1604,through the ADC 1603, through the first AM 1602 and into the anodechamber 1601 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1601.

Following passage through 1606, the liquid is then passed through thecomposite anion-cation exchange material layer 1607 of the triple layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1607. The compositeanion-cation exchange material layer 1607 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1608, through the CDC 1609, and through the secondCM 1610 and into the cathode chamber 1611 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1611. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1604, through the ADC 1603, through the first AM 1602 andinto the anode chamber 1601 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1601.

Example 7

An EDI device as shown in FIG. 16 was constructed using machined highdensity polyethylene hardware to retain the electrodes, membranes andresin. The internal flow dimensions of the ADC were 1.27 cm in diameterand 3.81 cm in length. The internal flow dimensions of the LDC were 1.27cm in diameter and 1.27 cm in length. The internal flow dimensions ofthe CDC were 1.27 cm in diameter and 3.81 cm in length.

The anode chamber 1601 contained platinum gauze electrodes (Unique WireWeaving Inc, Hillside, N.J.). In contact with the anode and separatingthe anode chamber 1601 from the ADC 1603 was an AM 1602 (AMI-7001, aproduct of Membranes International, Glen Rock, N.J.). The ADC 1603 wasfilled with an anion exchange resin (DOWEX™ 1x4 (200 mesh), a product ofThe Dow Chemical Company, Midland, Mich.) in the hydroxide form. An AM1604 (AMI-7001, a product of Membranes International, Glen Rock, N.J.)separated the ADC 1603 from the LDC. The LDC contained a 0.4 cm dopedanion exchange resin layer 1605 comprising an anion exchange resin(DOWEX™ 1x4 (200 mesh), a product of The Dow Chemical Company, Midland,Mich.) doped with a cation exchange resin (DOWEX™ 50Wx4 (200 mesh), aproduct of The Dow Chemical Company, Midland, Mich.), a 0.4 cm dopedcation exchange layer 1606 comprising a cation exchange resin (DOWEX™50Wx4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.)doped with an anion exchange resin (DOWEX™ 1x4 (200 mesh), a product ofThe Dow Chemical Company, Midland, Mich.) and a 0.5 cm (approximate)composite bed ion exchange layer 1607 comprising a mixture of anionexchange resin (DOWEX™ 1x4 (200 mesh), a product of The Dow ChemicalCompany, Midland, Mich.) and cation exchange resin (DOWEX™ 50Wx4 (200mesh), a product of The Dow Chemical Company, Midland, Mich.). The dopedanion exchange resin layer 1605 had an equivalence ratio of 4:1, anionto cation. The doped cation resin layer 1606 had an equivalence ratio of4:1, cation to anion. The composite bed ion exchange layer 1607contained a composite with an equivalence ratio of 1:1 anion to cationresin. The cation and anion exchange resins were in the hydronium andhydroxide forms, respectively. Separating the CDC 1609 from the LDC wasa CM 1608 (CMI-7000, a product of Membranes International, Glen Rock,N.J.). The CDC 1609 was filled with a cation exchange resin (DOWEX™50Wx4 (200 mesh), a product of The Dow Chemical Company, Midland,Mich.). The CDC 1609 was separated from the cathode chamber 1611 by a CM1610 (CMI-7000, a product of Membranes International, Glen Rock, N.J.).The cathode chamber 1611 contained platinum gauze electrodes (UniqueWire Weaving Inc, Hillside, N.J.). The cathode is in direct contact withthe CM 1610 separating the CDC 1609 and cathode chamber 1611. A pump(GP40, a product of Dionex, Sunnyvale, Calif.) was used to deliver ROquality water (specific conductance 12.3 μS/cm) at a flow rate of 2.0mL/min to the EDI device shown in FIG. 16. A conductivity detector(CD20, a product of Dionex, Sunnyvale, Calif.) with a flow cell was usedfor the conductivity measurements. From the pump, the RO water flow wasdirected to the CDC 1609, then the ADC 1603, to the doped anion layer1605 inlet of the LDC, through the doped cation layer 1606 of the LDC,and finally through the composite bed layer 1607 outlet and then to theflow through conductivity cell. A peristaltic pump (MASTERFLEX LS, aproduct of the Cole-Parmer company, Vernon Hills, Ill.) was used todeliver deionized water at a flow rate of 2.0 mL/min to the anodechamber 1601 and then to the cathode chamber 1611 and then to waste.

Initially, the conductance of the water exiting the EDI device was 2.9μS/cm. Using a laboratory power supply, (E3612A, a product of Agilent,Santa Clara, Calif.) a constant current of 40 mA was applied and theinitial voltage was 52V. Gas evolution was observed immediately from theanode and cathode chambers. The initial background conductivity of theproduct water increased to 32 gS/cm and over a 1 hour period theconductivity decreased to 0.63 μS/cm. The EDI device was allowed tooperate continuously for 7 days. The data in Table 10 shows results forthe device of FIG. 16.

TABLE 10 Conductance Measurements vs. Time Conductivity Hours Voltage(μS/cm) 0.0 0.0 2.9 1 45 0.66 2 42 0.35 10 40 0.12 24 32 0.074 48 260.057 72 24 0.055 96 25 0.056 120 25 0.055 144 27 0.056 168 29 0.055

Another method (not shown) for performing electrodeionization utilizingthe apparatus as illustrated in FIG. 16 comprises directing the flowthrough the apparatus in essentially a mirror image flow pattern. Theliquid may be initially directed through the ADC 1603. The ADC 1603 mayremove most of the anions from the liquid. The anions are attracted tothe anode by the applied electric field. The anions may pass through thefirst AM 1602 and into the anode chamber 1601 where they may be removedfrom the apparatus by the waste liquid stream that removes ions from theanode chamber 1601. Remaining cations will be attracted to the cathode.The cations will be retained in the liquid because they will not passthrough the second AM 1604 that forms the cathode side of the ADC 1603.

Following passage through 1603, the liquid may then flow through the CDC1609. The CDC 1609 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1610 and into the cathode chamber1611 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1611. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1608 that forms theanode side of the CDC 1609.

Following passage through 1609, the liquid may then pass through thetriple layer depletion chamber. The liquid is passed through the dopedanion exchange material layer 1605 of the triple layer depletion chamberby placing the inlet portion of the chamber above the doped anionexchange material layer 1605. The doped anion exchange material layermay remove remaining anions from the liquid. Anions are attracted to theanode by the applied electric field. The anions may pass through thesecond AM 1604, through the ADC 1603, and through the first AM 1602 andinto the anode chamber 1601 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1601. The cations will be attracted to the cathode by the appliedelectric field. Some of the cations may be retained by the cation ionexchange material used as a dopant and may be allowed to pass throughthe first CM 1608, through the CDC 1609, through the second CM 1610 andinto the cathode chamber 1611 where they may be removed from theapparatus by the waste liquid stream that removes ions from the cathodechamber 1611.

Following passage through 1605, the liquid is then passed through thedoped cation exchange material layer 1606 of the triple layer depletionchamber. The doped cation exchange material layer 1606 may removeremaining cations from the liquid. Cations are attracted to the cathodeby the applied electric field. The cations may pass through the first CM1608, through the CDC 1609, and through the second CM 1610 and into thecathode chamber 1611 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1611. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be retained by the anion ion exchange materialused as a dopant and may be allowed to pass through the second AM 1604,through the ADC 1603, through the first AM 1602 and into the anodechamber 1601 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1601.

Following passage through 1606, the liquid is then passed through thecomposite anion-cation exchange material layer 1607 of the triple layerdepletion chamber by placing the outlet portion of the chamber below thecomposite anion-cation exchange material layer 1607. The compositeanion-cation exchange material layer 1607 may be effective at removingboth remaining anions and cations. The remaining cations are attractedto the cathode by the applied electric field. The cations may passthrough the first CM 1608, through the CDC 1609, and through the secondCM 1610 and into the cathode chamber 1611 where they may be removed fromthe apparatus by the waste liquid stream that removes ions from thecathode chamber 1611. The remaining anions are attracted to the anode bythe applied electric field. The anions may be allowed to pass throughthe second AM 1604, through the ADC 1603, through the first AM 1602 andinto the anode chamber 1601 where they may be removed from the apparatusby the waste liquid stream that removes ions from the anode chamber1601.

Two additional methods for performing electrodeionization (not shown) onthe apparatus as illustrated in FIG. 16 may be realized by switching theinlet and outlet of the triple layer depletion chamber. In oneadditional method, the liquid may be initially directed through the CDC1609. The CDC 1609 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1610 and into the cathode chamber1611 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1611. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1608 that forms theanode side of the CDC 1609.

Following passage through 1609, the liquid may then flow through the ADC1603. The ADC 1603 may remove most of the anions from the liquid. Theanions are attracted to the anode by the applied electric field. Theanions may pass through the first AM 1602 and into the anode chamber1601 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1601. Remaining cationswill be attracted to the cathode. The cations will be retained in theliquid because they will not pass through the second AM 1604 that formsthe cathode side of the ADC 1603.

Following passage through 1603, the liquid is then passed through thecomposite anion-cation exchange material layer 1607 of the triple layerdepletion. The composite anion-cation exchange material layer 1607 maybe effective at removing both remaining anions and cations. Theremaining cations are attracted to the cathode by the applied electricfield. The cations may pass through the first CM 1608, through the CDC1609, and through the second CM 1610 and into the cathode chamber 1611where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1611. The remaining anionsare attracted to the anode by the applied electric field. The anions maybe allowed to pass through the second AM 1604, through the ADC 1603,through the first AM 1602 and into the anode chamber 1601 where they maybe removed from the apparatus by the waste liquid stream that removesions from the anode chamber 1601.

Following passage through 1607, the liquid is then passed through thedoped cation exchange material layer 1606 of the triple layer depletionchamber. The doped cation exchange material layer 1606 may removeremaining cations from the liquid. Cations are attracted to the cathodeby the applied electric field. The cations may pass through the first CM1608, through the CDC 1609, and through the second CM 1610 and into thecathode chamber 1611 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1611. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be retained by the anion ion exchange materialused as a dopant and may be allowed to pass through the second AM 1604,through the ADC 1603, through the first AM 1602 and into the anodechamber 1601 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1601.

Following passage through 1606, the liquid may then pass through thedoped anion exchange material layer 1605 of the triple layer depletionchamber. The doped anion exchange material layer may remove remaininganions from the liquid. Anions are attracted to the anode by the appliedelectric field. The anions may pass through the second AM 1604, throughthe ADC 1603, and through the first AM 1602 and into the anode chamber1601 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1601. The cations willbe attracted to the cathode by the applied electric field. Some of thecations may be retained by the cation ion exchange material used as adopant and may be allowed to pass through the first CM 1608, through theCDC 1609, through the second CM 1610 and into the cathode chamber 1611where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1611.

Another additional method (not shown) for performing electrodeionizationutilizing the apparatus as illustrated in FIG. 16 comprises directingthe flow through the apparatus in an alternate flow pattern. The liquidmay be initially directed through the ADC 1603. The ADC 1603 may removemost of the anions from the liquid. The anions are attracted to theanode by the applied electric field. The anions may pass through thefirst AM 1602 and into the anode chamber 1601 where they may be removedfrom the apparatus by the waste liquid stream that removes ions from theanode chamber 1601. Remaining cations will be attracted to the cathode.The cations will be retained in the liquid because they will not passthrough the second AM 1604 that forms the cathode side of the ADC 1603.

Following passage through 1603, the liquid may then flow through the CDC1609. The CDC 1609 may remove most of the cations from the liquid. Thecations are attracted to the cathode by the applied electric field. Thecations may pass through the second CM 1610 and into the cathode chamber1611 where they may be removed from the apparatus by the waste liquidstream that removes ions from the cathode chamber 1611. Anions will beattracted to the anode. The anions will be retained in the liquidbecause they will not pass through the first CM 1608 that forms theanode side of the CDC 1609.

Following passage through 1609, the liquid is then passed through thecomposite anion-cation exchange material layer 1607 of the triple layerdepletion. The composite anion-cation exchange material layer 1607 maybe effective at removing both remaining anions and cations. Theremaining cations are attracted to the cathode by the applied electricfield. The cations may pass through the first CM 1608, through the CDC1609, and through the second CM 1610 and into the cathode chamber 1611where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1611. The remaining anionsare attracted to the anode by the applied electric field. The anions maybe allowed to pass through the second AM 1604, through the ADC 1603,through the first AM 1602 and into the anode chamber 1601 where they maybe removed from the apparatus by the waste liquid stream that removesions from the anode chamber 1601.

Following passage through 1607, the liquid is then passed through thedoped cation exchange material layer 1606 of the triple layer depletionchamber. The doped cation exchange material layer 1606 may removeremaining cations from the liquid. Cations are attracted to the cathodeby the applied electric field. The cations may pass through the first CM1608, through the CDC 1609, and through the second CM 1610 and into thecathode chamber 1611 where they may be removed from the apparatus by thewaste liquid stream that removes ions from the cathode chamber 1611. Theanions will be attracted to the anode by the applied electric field.Some of the anions may be retained by the anion ion exchange materialused as a dopant and may be allowed to pass through the second AM 1604,through the ADC 1603, through the first AM 1602 and into the anodechamber 1601 where they may be removed from the apparatus by the wasteliquid stream that removes ions from the anode chamber 1601.

Following passage through 1606, the liquid may then pass through thedoped anion exchange material layer 1605 of the triple layer depletionchamber. The doped anion exchange material layer may remove remaininganions from the liquid. Anions are attracted to the anode by the appliedelectric field. The anions may pass through the second AM 1604, throughthe ADC 1603, and through the first AM 1602 and into the anode chamber1601 where they may be removed from the apparatus by the waste liquidstream that removes ions from the anode chamber 1601. The cations willbe attracted to the cathode by the applied electric field. Some of thecations may be retained by the cation ion exchange material used as adopant and may be allowed to pass through the first CM 1608, through theCDC 1609, through the second CM 1610 and into the cathode chamber 1611where they may be removed from the apparatus by the waste liquid streamthat removes ions from the cathode chamber 1611.

The foregoing descriptions of exemplary embodiments of the presentinvention have been presented for the purpose of illustration anddescription. They are not intended to be exhaustive or to limit thepresent invention to the precise forms disclosed, and obviously manymodifications, embodiments, and variations are possible in light of theabove teaching.

1. An electrodeionization apparatus comprising: a. an anode chamber 201,including an anode therein; b. a cathode chamber 206, including acathode therein; i. wherein, an electric field is formed as a result ofa voltage applied between the anode and the cathode; c. an anionmembrane 202 contiguous with the anode chamber 201; d. a dual layerdepletion chamber comprising; i. an anion exchange material layer 203contiguous with the anion membrane 202, the anion exchange materiallayer including therein anion exchange materials; ii. a compositeanion-cation exchange material layer 204 contiguous with the anionexchange material layer 203, the composite anion-cation exchangematerial layer including therein one of a mixed ion exchange material,or a doped anion exchange material, or a doped cation exchange material;iii. wherein the interface between the anion exchange material layer 203and the composite anion-cation exchange material layer 204 issubstantially transverse to the applied electric field; and a cationmembrane 205 contiguous with the composite anion-cation exchangematerial layer 204 of the dual layer depletion chamber and contiguouswith the cathode chamber
 206. 2. An electrodeionization apparatuscomprising: a. an anode chamber 301, including an anode therein; b. acathode chamber 306, including a cathode therein; i. wherein, anelectric field is formed as a result of a voltage applied between theanode and the cathode; c. an anion membrane 302 contiguous with theanode chamber 301; d. a dual layer depletion chamber comprising; i. acomposite anion-cation exchange material layer 303 contiguous with theanion membrane 302, the composite anion-cation exchange material layerincluding therein one of a mixed ion exchange material, or a doped anionexchange material, or a doped cation exchange material; ii. a cationexchange material layer 304 contiguous with the composite anion-cationexchange material layer 303, the cation exchange material layerincluding therein cation exchange materials; iii. wherein the interfacebetween the composite anion-cation exchange material layer 303 and thecation exchange material layer 304 is substantially transverse to theapplied electric field; and e. a cation membrane 305 contiguous with thecation exchange material layer 304 of the dual layer depletion chamberand contiguous with the cathode chamber
 306. 3. An electrodeionizationapparatus comprising: a. an anode chamber 401, including an anodetherein; b. a cathode chamber 407, including a cathode therein; i.wherein, an electric field is formed as a result of a voltage appliedbetween the anode and the cathode; c. an anion membrane 402 contiguouswith the anode chamber 401; d. an anion exchange material layer 403contiguous with the anion membrane 402, the anion exchange materiallayer including therein anion exchange materials; e. a compositeanion-cation exchange material layer 404 contiguous with the anionexchange material layer 403, the composite anion-cation exchangematerial layer including therein one of a mixed ion exchange material,or a doped anion exchange material, or a doped cation exchange material;i. wherein the interface between the anion exchange material layer 403and the composite anion-cation exchange material layer 404 issubstantially transverse to the applied electric field; f. a cationexchange material layer 405 contiguous with the composite anion-cationexchange material layer 404, the cation exchange material layerincluding therein cation exchange materials; i. wherein the interfacebetween the composite anion-cation exchange material layer 404 and thecation exchange material layer 405 is substantially transverse to theapplied electric field; and g. a cation membrane 406 contiguous with thecation exchange material layer 405 and contiguous with the cathodechamber
 407. 4. An electrodeionization apparatus comprising: a. an anodechamber 511, including an anode therein; b. a cathode chamber 518,including a cathode therein; i. wherein, an electric field is formed asa result of a voltage applied between the anode and the cathode; c. ananion membrane 512 contiguous with the anode chamber 511; d. a firstcomposite anion-cation exchange material layer 513 contiguous with theanion membrane 512, the first composite anion-cation exchange materiallayer including therein one of a mixed ion exchange material, or a dopedanion exchange material, or a doped cation exchange material; e. ananion exchange material layer 514 contiguous with the first compositeanion-cation exchange material layer 513, the anion exchange materiallayer comprising anion exchange materials; i. wherein the interfacebetween the first composite anion-cation exchange material layer 513 andthe anion exchange material layer 514 is substantially transverse to theapplied electric field; f. a second composite anion-cation exchangematerial layer 515 contiguous with the anion exchange material layer514, the second composite anion-cation exchange material layer includingtherein one of a mixed ion exchange material, or a doped anion exchangematerial, or a doped cation exchange material; i. wherein the interfacebetween the anion exchange material layer 514 and the second compositeanion-cation exchange material layer 515 is substantially transverse tothe applied electric field; g. a cation exchange material layer 516contiguous with the second composite anion-cation exchange materiallayer 515, the cation exchange material layer including therein cationexchange materials; i. wherein the interface between the secondcomposite anion-cation exchange material layer 515 and the cationexchange material layer 516 is substantially transverse to the appliedelectric field; and h. a cation membrane 517 contiguous with the cationexchange material layer 516 and contiguous with the cathode chamber 518.5. An electrodeionization apparatus comprising: a. an anode chamber 501including an anode therein; b. a cathode chamber 508, including acathode therein; i. wherein, an electric field is formed as a result ofa voltage applied between the anode and the cathode; c. an anionmembrane 502 contiguous with the anode chamber 501; d. an anion exchangematerial layer 503 contiguous with the anion membrane 502, the anionexchange material layer including therein anion exchange materials; e. afirst composite anion-cation exchange material layer 504 contiguous withthe anion exchange material layer 503, the first composite anion-cationexchange material layer including therein one of a mixed ion exchangematerial, or a doped anion exchange material, or a doped cation exchangematerial; i. wherein the interface between the anion exchange materiallayer 503 and the first composite anion-cation exchange material layer504 is substantially transverse to the applied electric field; f. acation exchange material layer 505 contiguous with the first compositeanion-cation exchange material layer 504, the cation exchange materiallayer including therein cation exchange materials; i. wherein theinterface between the first composite anion-cation exchange materiallayer 504 and the cation exchange material layer 505 is substantiallytransverse to the applied electric field; g. a second compositeanion-cation exchange material layer 506 contiguous with the cationexchange material layer 505, the second composite anion-cation exchangematerial layer including therein one of a mixed ion exchange material,or a doped anion exchange material, or a doped cation exchange material;i. wherein the interface between the cation exchange material layer 505and the second composite anion-cation exchange material layer 506 issubstantially transverse to the applied electric field; and a cationmembrane 507 contiguous with the second composite anion-cation exchangematerial layer 506 and contiguous with the cathode chamber
 508. 6. Anelectrodeionization apparatus comprising: a. an anode chamber 601,including an anode therein; b. a cathode chamber 608, including acathode therein; i. wherein, an electric field is formed as a result ofa voltage applied between the anode and the cathode; c. an anionmembrane 602 contiguous with the anode chamber 601; d. a dual layerdepletion chamber comprising; i. an anion exchange material layer 603contiguous with the anion membrane 602, the anion exchange materiallayer including therein anion exchange materials; ii. a compositeanion-cation exchange material layer 604 contiguous with the anionexchange material layer 603, the composite anion-cation exchangematerial layer including therein one of a mixed ion exchange material,or a doped anion exchange material, or a doped cation exchange material;iii. wherein the interface between the anion exchange material layer 603and the composite anion-cation exchange material layer 604 issubstantially transverse to the applied electric field; e. a firstcation membrane 605 contiguous with the composite anion-cation exchangematerial layer 604 of the dual layer depletion chamber; f. a cationexchange material layer 606 contiguous with the first cation membrane605, the cation exchange material layer including therein cationexchange materials; g. a second cation membrane 607 contiguous with thecation exchange material layer 606 and contiguous with the cathodechamber
 608. 7. An electrodeionization apparatus comprising: a. an anodechamber 701, including an anode therein; b. a cathode chamber 708,including a cathode therein; i. wherein, an electric field is formed asa result of a voltage applied between the anode and the cathode; c. afirst anion membrane 702 contiguous with the anode chamber 701; d. ananion depletion chamber 703 contiguous with the first anion membrane702, the anion depletion chamber including therein anion exchangematerials; e. a second anion membrane 704 contiguous with the aniondepletion chamber 703; f. a dual layer depletion chamber comprising; i.a composite anion-cation exchange material layer 705 contiguous with thesecond anion membrane 704, the composite anion-cation exchange materiallayer including therein one of a mixed ion exchange material, or a dopedanion exchange material, or a doped cation exchange material; ii. acation exchange material layer 706 contiguous with the compositeanion-cation exchange material layer 705, the cation exchange materiallayer including therein cation exchange materials; iii. wherein theinterface between the composite anion-cation exchange material layer 705and the cation exchange material layer 706 is substantially transverseto the applied electric field; and g. a cation membrane 707 contiguouswith the cation exchange material layer 706 of the dual layer depletionchamber and contiguous with the cathode chamber
 708. 8. Anelectrodeionization apparatus comprising: a. an anode chamber 801,including an anode therein; b. a cathode chamber 810, including acathode therein; i. wherein, an electric field is formed as a result ofa voltage applied between the anode and the cathode; c. a first cationmembrane 802 contiguous with the anode chamber; d. a cation depletionchamber 803 contiguous with the first cation membrane 802, the cationdepletion chamber including therein cation exchange materials; e. asecond cation membrane 804 contiguous with the cation depletion chamber803; f. a composite bed concentrate chamber 805 contiguous with thesecond cation membrane 804, the composite bed depletion chamberincluding therein one of a mixed ion exchange material, or a doped anionexchange material, or a doped cation exchange material; g. an anionmembrane 806 contiguous with the composite bed concentrate chamber 805;h. a dual layer depletion chamber comprising; i. an anion exchangematerial layer 807 contiguous with the anion membrane 806, the anionexchange material layer including therein anion exchange materials; ii.a composite anion-cation exchange material layer 808 contiguous with theanion exchange material layer 807, the composite anion-cation exchangematerial layer including therein one of a mixed ion exchange material,or a doped anion exchange material, or a doped cation exchange material;iii. wherein the interface between the anion exchange material layer 807and the composite anion-cation exchange material layer 808 issubstantially transverse to the applied electric field; and i. a thirdcation membrane 809 contiguous with the composite anion-cation exchangematerial layer 808 of the dual layer depletion chamber and contiguouswith the cathode chamber
 810. 9. An electrodeionization apparatuscomprising: a. an anode chamber 901, including an anode therein; b. acathode chamber 910, including a cathode therein; i. wherein, anelectric field is formed as a result of a voltage applied between theanode and the cathode c. a first anion membrane 902 contiguous with theanode chamber; d. a dual layer depletion chamber comprising; i. acomposite anion-cation exchange material layer 903 contiguous with thefirst anion membrane 902, the composite anion-cation exchange materiallayer including therein one of a mixed ion exchange material, or a dopedanion exchange material, or a doped cation exchange material; ii. acation exchange material layer 904 contiguous with the compositeanion-cation exchange material layer 903, the cation exchange materiallayer including therein cation exchange materials; iii. wherein theinterface between the composite anion-cation exchange material layer 903and the cation exchange material layer 904 is substantially transverseto the applied electric field; e. a cation membrane 905 contiguous withthe cation exchange material layer 904 of the dual layer depletionchamber; f. a composite bed concentrate chamber 906 contiguous with thefirst cation membrane 905, the composite bed concentrate chamberincluding therein one of a mixed ion exchange material, or a doped anionexchange material, or a doped cation exchange material; g. a secondanion membrane 907 contiguous with the composite bed depletion chamber906; h. an anion depletion chamber 908 contiguous with the second anionmembrane 907, the anion depletion chamber including therein anionexchange materials; and i. a third anion membrane 909 contiguous withthe anion depletion chamber 908 and contiguous with the cathode chamber910.
 10. An electrodeionization apparatus comprising: a. an anodechamber 1001, including an anode therein; b. a cathode chamber 1010,including a cathode therein; i. wherein, an electric field is formed asa result of a voltage applied between the anode and the cathode; c. afirst anion membrane 1002 contiguous with the anode chamber 1001; d. ananion depletion chamber 1003 contiguous with the first anion membrane1002, the anion depletion chamber including therein anion exchangematerials; e. a second anion membrane 1004 contiguous with the aniondepletion chamber 1003; f. a dual layer depletion chamber contiguouswith the second anion membrane, the dual layer depletion chambercomprising; i. a cation exchange material layer 1005 disposed at theinlet of the dual layer depletion chamber, the cation exchange materiallayer including therein cation exchange materials; ii. a compositeanion-cation exchange material layer 1006 disposed at the outlet of thedual layer depletion chamber, the composite anion-cation exchangematerial layer including therein one of a mixed ion exchange material,or a doped anion exchange material, or a doped cation exchange material;iii. wherein the cation exchange material layer 1005 and the compositeanion-cation exchange material layer 1006 are in contiguous contact; iv.wherein the interface between the cation exchange material layer 1005and the composite anion-cation exchange material layer 1006 issubstantially parallel to the applied electric field; g. a first cationmembrane 1007 contiguous with the dual layer depletion chamber; h. ancation depletion chamber 1008 contiguous with the first cation membrane1007, the cation depletion chamber including therein cation exchangematerials; and i. a second cation membrane 1009 contiguous with thecation depletion chamber 1008 and contiguous with the cathode chamber1010.
 11. An electrodeionization apparatus comprising: a. an anodechamber 1101, including an anode therein; b. a cathode chamber 1110,including a cathode therein; i. wherein, an electric field is formed asa result of a voltage applied between the anode and the cathode; c. afirst anion membrane 1102 contiguous with the anode chamber; d. an aniondepletion chamber 1103 contiguous with the first anion membrane 1102,the anion depletion chamber including therein anion exchange materials;e. a second anion membrane 1104 contiguous with the anion depletionchamber 1103; f. a dual layer depletion chamber contiguous with thesecond anion membrane, the dual layer depletion chamber comprising; i.an anion exchange material layer 1105 disposed at the inlet of the duallayer depletion chamber, the anion exchange material layer includingtherein anion exchange materials; ii. a composite anion-cation exchangematerial layer 1106 disposed at the outlet of the dual layer depletionchamber, the composite anion-cation exchange material layer includingtherein one of a mixed ion exchange material, or a doped anion exchangematerial, or a doped cation exchange material; iii. wherein the anionexchange material layer 1105 and the composite anion-cation exchangematerial layer 1106 are in contiguous contact; iv. wherein the interfacebetween the anion exchange material layer 1105 and the compositeanion-cation exchange material layer 1106 is substantially parallel tothe applied electric field; g. a first cation membrane 1107 contiguouswith the dual layer depletion chamber; h. an cation depletion chamber1108 contiguous with the first cation membrane 1107, the cationdepletion chamber including therein cation exchange materials; and i. asecond cation membrane 1109 contiguous with the cation depletion chamber1108 and contiguous with the cathode chamber
 1110. 12. Anelectrodeionization apparatus comprising: a. an anode chamber 1201;including an anode therein; b. a cathode chamber 1211, including acathode therein; i. wherein, an electric field is formed as a result ofa voltage applied between the anode and the cathode; c. a first anionmembrane 1202 contiguous with the anode chamber 1201; d. an aniondepletion chamber 1203 contiguous with the first anion membrane 1202,the anion depletion chamber including therein anion exchange materials;e. a second anion membrane 1204 contiguous with the anion depletionchamber 1203; f. a triple layer depletion chamber contiguous with thefirst cation membrane, the triple layer depletion chamber comprising; i.a cation exchange material layer 1205 disposed at the inlet of thetriple layer depletion chamber, the cation exchange material layerincluding therein cation exchange materials; ii. an anion exchangematerial layer 1206 disposed at the center of the triple layer depletionchamber, the anion exchange material layer including therein anionexchange materials; iii. a composite anion-cation exchange materiallayer 1207 disposed at the outlet of the triple layer depletion chamber,the composite anion-cation exchange material layer including therein oneof a mixed ion exchange material, or a doped anion exchange material, ora doped cation exchange material; iv. wherein the cation exchangematerial layer 1205 and the anion exchange material layer 1206 are incontiguous contact; v. wherein the anion exchange material layer 1206and the composite anion-cation exchange material layer 1207 are incontiguous contact; vi. wherein the interface between the cationexchange material layer 1205 and the anion exchange material layer 1206is substantially parallel to the applied electric field; vii. whereinthe interface between the anion exchange material layer 1206 and thecomposite anion-cation exchange material layer 1207 is substantiallyparallel to the applied electric field; g. a first cation membrane 1208contiguous with the triple layer depletion chamber; h. a cationdepletion chamber 1209 contiguous with the first cation membrane 1208,the cation depletion chamber including therein cation exchangematerials; and i. a second cation membrane 1210 contiguous with thecation depletion chamber 1209 and contiguous with the cathode chamber1211.
 13. An electrodeionization apparatus comprising: a. an anodechamber 1301, including an anode therein; b. a cathode chamber 1310,including a cathode therein; i. wherein, an electric field is formed asa result of a voltage applied between the anode and the cathode; c. afirst anion membrane 1302 contiguous with the anode chamber 1301; d. ananion depletion chamber 1303 contiguous with the first anion membrane1302, the anion depletion chamber including therein anion exchangematerials; e. a second anion membrane 1304 contiguous with the aniondepletion chamber 1303; f. a dual layer depletion chamber contiguouswith the first cation membrane, the dual layer depletion chambercomprising; i. a doped anion exchange material layer 1305 disposed atthe inlet of the dual layer depletion chamber, the doped anion exchangematerial layer including therein a composite of anion and cationexchange materials wherein the anion exchange material is responsiblefor at least about 60% of the total ion exchange capacity and theremainder of the total ion exchange capacity is contributed by thecation exchange material; ii. a doped cation exchange material layer1306 disposed at the outlet of the dual layer depletion chamber, thedoped cation exchange material layer including therein a composite ofanion and cation exchange materials wherein the cation exchange materialis responsible for at least about 60% of the total ion exchange capacityand the remainder of the total ion exchange capacity is contributed byanion exchange material; iii. wherein the doped anion exchange materiallayer 1305 and the doped cation exchange material layer 1306 are incontiguous contact; iv. wherein the interface between the doped anionexchange material layer 1305 and the doped cation exchange materiallayer 1306 is substantially parallel to the applied electric field; g. afirst cation membrane 1307 contiguous with the dual layer depletionchamber; h. an cation depletion chamber 1308 contiguous with the firstcation membrane 1307, the cation depletion chamber including thereincation exchange materials; and i. a second cation membrane 1309contiguous with the cation depletion chamber 1308 and contiguous withthe cathode chamber
 1310. 14. An electrodeionization apparatuscomprising: a. an anode chamber 1401, including an anode therein; b. acathode chamber 1410, including a cathode therein; i. wherein, anelectric field is formed as a result of a voltage applied between theanode and the cathode; c. a first anion membrane 1402 contiguous withthe anode chamber 1401; d. an anion depletion chamber 1403 contiguouswith the first anion membrane 1402, the anion depletion chamberincluding therein anion exchange materials; e. a second anion membrane1404 contiguous with the anion depletion chamber 1403; f. a dual layerdepletion chamber contiguous with the first cation membrane, the duallayer depletion chamber comprising; i. a doped anion exchange materiallayer 1405 disposed at the inlet of the dual layer depletion chamber,the doped anion exchange material layer including therein a composite ofanion and cation exchange materials wherein the anion exchange materialis responsible for at least about 60% of the total ion exchange capacityand the remainder of the total ion exchange capacity is contributed bythe cation exchange material; ii. a composite anion-cation exchangematerial layer 1406 disposed at the outlet of the dual layer depletionchamber, the composite anion-cation exchange material layer includingtherein a mixed ion exchange material, or a doped anion exchangematerial, or a doped cation exchange material; iii. wherein the dopedanion exchange material layer 1405 and the composite anion-cationexchange material layer 1406 are in contiguous contact; iv. wherein theinterface between the doped anion exchange material layer 1405 and thecomposite anion-cation exchange material layer 1406 is substantiallyparallel to the applied electric field; g. a first cation membrane 1407contiguous with the dual layer depletion chamber; h. an cation depletionchamber 1408 contiguous with the first cation membrane 1407, the cationdepletion chamber including therein cation exchange materials; and i. asecond cation membrane 1409 contiguous with the cation depletion chamber1408 and contiguous with the cathode chamber
 1410. 15. Anelectrodeionization apparatus comprising: a. an anode chamber 1501,including an anode therein; b. a cathode chamber 1510, including acathode therein; i. wherein, an electric field is formed as a result ofa voltage applied between the anode and the cathode; c. a first anionmembrane 1502 contiguous with the anode chamber 1501; d. an aniondepletion chamber 1503 contiguous with the first anion membrane 1502,the anion depletion chamber including therein anion exchange materials;e. a second anion membrane 1504 contiguous with the anion depletionchamber 1503; f. a dual layer depletion chamber contiguous with thefirst cation membrane, the dual layer depletion chamber comprising; i. adoped cation exchange material layer 1505 disposed at the inlet of thedual layer depletion chamber, the doped cation exchange material layerincluding therein a composite of anion and cation exchange materialswherein the cation exchange material is responsible for at least about60% of the total ion exchange capacity and the remainder of the totalion exchange capacity is contributed by anion exchange material; ii. acomposite anion-cation exchange material layer 1506 disposed at theoutlet of the dual layer depletion chamber, the composite anion-cationexchange material layer including therein one of a mixed ion exchangematerial, or a doped anion exchange material, or a doped cation exchangematerial; iii. wherein the doped cation exchange material layer 1505 andthe composite anion-cation exchange material layer 1506 are incontiguous contact; iv. wherein the interface between the doped cationexchange material layer 1505 and the composite anion-cation exchangematerial layer 1506 is substantially parallel to the applied electricfield; g. a first cation membrane 1507 contiguous with the dual layerdepletion chamber; h. a cation depletion chamber 1508 contiguous withthe first cation membrane 1507, the cation depletion chamber includingtherein cation exchange materials; and i. a second cation membrane 1509contiguous with the cation depletion chamber 1508 and contiguous withthe cathode chamber
 1510. 16. An electrodeionization apparatuscomprising: a. an anode chamber 1601, including an anode therein; b. acathode chamber 1611, including a cathode therein; i. wherein, anelectric field is formed as a result of a voltage applied between theanode and the cathode; c. a first anion membrane 1602 contiguous withthe anode chamber 1601; d. an anion depletion chamber 1603 contiguouswith the first anion membrane 1602, the anion depletion chamberincluding therein anion exchange materials; e. a second anion membrane1604 contiguous with the anion depletion chamber 1603; f. a triple layerdepletion chamber contiguous with the first cation membrane, the triplelayer depletion chamber comprising; i. a doped anion exchange materiallayer 1605 disposed at the inlet of the triple layer depletion chamber,the anion exchange material layer including therein a composite of anionand cation exchange materials wherein the anion exchange material isresponsible for at least about 60% of the total ion exchange capacityand the remainder of the total ion exchange capacity is contributed bythe cation exchange material; ii. a doped cation exchange material layer1606 disposed at the center of the triple layer depletion chamber, thecation exchange material layer including therein a composite of anionand cation exchange materials wherein the cation exchange material isresponsible for at least about 60% of the total ion exchange capacityand the remainder of the total ion exchange capacity is contributed byanion exchange material; iii. a composite anion-cation exchange materiallayer 1607 disposed at the outlet of the triple layer depletion chamber,the composite anion-cation exchange material layer including therein oneof a mixed ion exchange material, or a doped anion exchange material, ora doped cation exchange material; iv. wherein the doped anion exchangematerial layer 1605 and the doped cation exchange material layer 1606are in contiguous contact; v. wherein the doped cation exchange materiallayer 1606 and the composite anion-cation exchange material layer 1607are in contiguous contact; vi. wherein the interface between the dopedanion exchange material layer 1605 and the doped cation exchangematerial layer 1606 is substantially parallel to the applied electricfield; vii. wherein the interface between the doped cation exchangematerial layer 1606 and the composite anion-cation exchange materiallayer 1607 is substantially parallel to the applied electric field; g. afirst cation membrane 1608 contiguous with the triple layer depletionchamber; h. a cation depletion chamber 1609 contiguous with the firstcation membrane 1608, the cation depletion chamber including thereincation exchange materials; and i. a second cation membrane 1610contiguous with the cation depletion chamber 1609 and contiguous withthe cathode chamber 1611.